diff --git a/LibreOJ/106/106.cpp b/LibreOJ/106/106.cpp
new file mode 100644
index 00000000..353caf3f
--- /dev/null
+++ b/LibreOJ/106/106.cpp
@@ -0,0 +1,392 @@
+#include <iostream>
+#include <limits>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 5e4 + 5;
+
+class Splay {
+  private:
+    struct node {
+        int value;
+        node *lchild, *rchild, *parent, **root;
+        size_t size, count;
+
+        node()
+            : value(0), lchild(nullptr), rchild(nullptr), parent(nullptr), root(nullptr), size(0), count(0) {}
+
+        node(const int &_value, node *_parent, node **_root)
+            : value(_value), lchild(nullptr), rchild(nullptr), parent(_parent), root(_root), size(1), count(1) {}
+
+        ~node() {
+            if (lchild != nullptr) delete lchild;
+            if (rchild != nullptr) delete rchild;
+        }
+
+        node *&child(unsigned int x) {
+            return !x ? lchild : rchild;
+        }
+
+        unsigned relation() const {
+            return this == parent->lchild ? 0 : 1;
+        }
+
+        size_t lsize() const {
+            return lchild == nullptr ? 0 : lchild->size;
+        }
+
+        size_t rsize() const {
+            return rchild == nullptr ? 0 : rchild->size;
+        }
+
+        void pushup() {
+            size = lsize() + count + rsize();
+        }
+
+        void rotate() {
+            node *old = parent;
+            unsigned x = relation();
+
+            if (old->parent != nullptr) {
+                old->parent->child(old->relation()) = this;
+            }
+            parent = old->parent;
+
+            if (child(x ^ 1) != nullptr) {
+                child(x ^ 1)->parent = old;
+            }
+            old->child(x) = child(x ^ 1);
+
+            child(x ^ 1) = old;
+            old->parent = this;
+
+            old->pushup();
+            pushup();
+        }
+
+        void splay(node *target = nullptr) {
+            while (parent != target) {
+                if (parent->parent == target) {
+                    rotate();
+                } else if (relation() == parent->relation()) {
+                    parent->rotate();
+                    rotate();
+                } else {
+                    rotate();
+                    rotate();
+                }
+            }
+
+            if (target == nullptr) *root = this;
+        }
+
+        node *predecessor() {
+            node *pred = lchild;
+
+            while (pred->rchild != nullptr) {
+                pred = pred->rchild;
+            }
+
+            return pred;
+        }
+
+        node *successor() {
+            node *succ = rchild;
+
+            while (succ->lchild != nullptr) {
+                succ = succ->lchild;
+            }
+
+            return succ;
+        }
+    } * root;
+
+    node *_insert(const int &value) {
+        node **target = &root, *parent = nullptr;
+
+        while (*target != nullptr && (*target)->value != value) {
+            parent = *target;
+            parent->size++;
+
+            if (value < parent->value) {
+                target = &parent->lchild;
+            } else {
+                target = &parent->rchild;
+            }
+        }
+
+        if (*target == nullptr) {
+            *target = new node(value, parent, &root);
+        } else {
+            (*target)->count++;
+            (*target)->size++;
+        }
+
+        (*target)->splay();
+
+        return root;
+    }
+
+    node *find(const int &value) {
+        node *node = root;
+
+        while (node != nullptr && value != node->value) {
+            if (value < node->value) {
+                node = node->lchild;
+            } else {
+                node = node->rchild;
+            }
+        }
+
+        if (node != nullptr) {
+            node->splay();
+        }
+
+        return node;
+    }
+
+    void erase(node *u) {
+        if (u == nullptr) return;
+
+        if (u->count > 1) {
+            u->splay();
+            u->count--;
+            u->size--;
+
+            return;
+        }
+
+        node *pred = u->predecessor(),
+             *succ = u->successor();
+
+        pred->splay();
+        succ->splay(pred);
+
+        delete succ->lchild;
+        succ->lchild = nullptr;
+
+        succ->pushup();
+        pred->pushup();
+    }
+
+  public:
+    Splay()
+        : root(nullptr) {
+        insert(std::numeric_limits<int>::min());
+        insert(std::numeric_limits<int>::max());
+    }
+
+    ~Splay() {
+        delete root;
+    }
+
+    void insert(const int &value) {
+        _insert(value);
+    }
+
+    void erase(const int &value) {
+        erase(find(value));
+    }
+
+    unsigned rank(const int &value) {
+        node *node = find(value);
+
+        if (node == nullptr) {
+            node = _insert(value);
+            int res = node->lsize();
+            erase(node);
+
+            return res;
+        }
+
+        return node->lsize();
+    }
+
+    const int &predecessor(const int &value) {
+        node *node = find(value);
+
+        if (node == nullptr) {
+            node = _insert(value);
+            const int &result = node->predecessor()->value;
+            erase(node);
+            return result;
+        }
+
+        return node->predecessor()->value;
+    }
+
+    const int &successor(const int &value) {
+        node *node = find(value);
+
+        if (node == nullptr) {
+            node = _insert(value);
+            const int &result = node->successor()->value;
+            erase(node);
+            return result;
+        }
+
+        return node->successor()->value;
+    }
+};
+
+struct node : Splay {
+    int l, r;
+    node *lchild, *rchild;
+
+    node()
+        : l(0), r(0), lchild(nullptr), rchild(nullptr) {}
+
+    node(const int &_l, const int &_r)
+        : l(_l), r(_r), lchild(nullptr), rchild(nullptr) {}
+
+    ~node() {
+        if (lchild != nullptr) delete lchild;
+        if (rchild != nullptr) delete rchild;
+    }
+} * root;
+
+int n, m, a[N];
+
+void build(node *&u, int l, int r) {
+    u = new node(l, r);
+
+    for (int i = l; i <= r; i++) {
+        u->insert(a[i]);
+    }
+
+    if (l == r) return;
+
+    int mid = (l + r) >> 1;
+
+    build(u->lchild, l, mid);
+    build(u->rchild, mid + 1, r);
+}
+
+int query_rank(node *u, int l, int r, int x) {
+    if (l <= u->l && u->r <= r) {
+        return u->rank(x) - 1;
+    }
+
+    int mid = (u->l + u->r) >> 1;
+    int res = 0;
+
+    if (l <= mid) res += query_rank(u->lchild, l, r, x);
+    if (r > mid) res += query_rank(u->rchild, l, r, x);
+
+    return res;
+}
+
+int query_kth(int _l, int _r, int k) {
+    int l = -1e8, r = 1e8, res = -1;
+
+    while (l <= r) {
+        int mid = (l + r) >> 1;
+
+        if (query_rank(root, _l, _r, mid) + 1 <= k) {
+            l = mid + 1;
+            res = mid;
+        } else {
+            r = mid - 1;
+        }
+    }
+
+    return res;
+}
+
+void modify(node *u, int p, int x) {
+    u->erase(a[p]);
+    u->insert(x);
+
+    if (u->l == u->r) return;
+
+    int mid = (u->l + u->r) >> 1;
+
+    if (p <= mid) modify(u->lchild, p, x);
+    else modify(u->rchild, p, x);
+}
+
+int query_pre(node *u, int l, int r, int x) {
+    if (l <= u->l && u->r <= r) {
+        return u->predecessor(x);
+    }
+
+    int mid = (u->l + u->r) >> 1;
+    int res = std::numeric_limits<int>::min();
+
+    if (l <= mid) res = std::max(res, query_pre(u->lchild, l, r, x));
+    if (r > mid) res = std::max(res, query_pre(u->rchild, l, r, x));
+
+    return res;
+}
+
+int query_suf(node *u, int l, int r, int x) {
+    if (l <= u->l && u->r <= r) {
+        return u->successor(x);
+    }
+
+    int mid = (u->l + u->r) >> 1;
+    int res = std::numeric_limits<int>::max();
+
+    if (l <= mid) res = std::min(res, query_suf(u->lchild, l, r, x));
+    if (r > mid) res = std::min(res, query_suf(u->rchild, l, r, x));
+
+    return res;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> m;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> a[i];
+    }
+
+    build(root, 1, n);
+
+    while (m--) {
+        int op;
+
+        cin >> op;
+
+        if (op == 1) {
+            int l, r, x;
+
+            cin >> l >> r >> x;
+
+            cout << query_rank(root, l, r, x) + 1 << endl;
+        } else if (op == 2) {
+            int l, r, k;
+
+            cin >> l >> r >> k;
+
+            cout << query_kth(l, r, k) << endl;
+        } else if (op == 3) {
+            int p, x;
+
+            cin >> p >> x;
+
+            modify(root, p, x);
+            a[p] = x;
+        } else if (op == 4) {
+            int l, r, x;
+
+            cin >> l >> r >> x;
+
+            cout << query_pre(root, l, r, x) << endl;
+        } else {  // op == 5
+            int l, r, x;
+
+            cin >> l >> r >> x;
+
+            cout << query_suf(root, l, r, x) << endl;
+        }
+    }
+
+    delete root;
+
+    return 0;
+}
diff --git a/LibreOJ/106/data/input0.in b/LibreOJ/106/data/input0.in
new file mode 100644
index 00000000..644b3126
--- /dev/null
+++ b/LibreOJ/106/data/input0.in
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:978d778808df00757dab64bc3f210eb847a9cadd5e03e1499b936715cb4d488f
+size 384
diff --git a/LibreOJ/106/data/input0.out b/LibreOJ/106/data/input0.out
new file mode 100644
index 00000000..12ffa6ec
--- /dev/null
+++ b/LibreOJ/106/data/input0.out
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:3fc690a2b7ec69fc1c9b7fb0011aa3504cfb5a587c121b7bbc7cc7a8ea687bfd
+size 51
diff --git a/LibreOJ/106/data/input1.in b/LibreOJ/106/data/input1.in
new file mode 100644
index 00000000..17efeb2a
--- /dev/null
+++ b/LibreOJ/106/data/input1.in
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:180082e9e720c7df6276a23493c4a5195d60b0bc45cec93af595aa78a510f9a0
+size 940
diff --git a/LibreOJ/106/data/input1.out b/LibreOJ/106/data/input1.out
new file mode 100644
index 00000000..a380d94c
--- /dev/null
+++ b/LibreOJ/106/data/input1.out
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
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+size 56
diff --git a/LibreOJ/106/data/input2.in b/LibreOJ/106/data/input2.in
new file mode 100644
index 00000000..294faacd
--- /dev/null
+++ b/LibreOJ/106/data/input2.in
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:ae8cbba88bb86018314daee90fb1c70ffc29b43bbd42be14587177397e062a62
+size 2361
diff --git a/LibreOJ/106/data/input2.out b/LibreOJ/106/data/input2.out
new file mode 100644
index 00000000..99033044
--- /dev/null
+++ b/LibreOJ/106/data/input2.out
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
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diff --git a/LibreOJ/106/data/input3.in b/LibreOJ/106/data/input3.in
new file mode 100644
index 00000000..07350296
--- /dev/null
+++ b/LibreOJ/106/data/input3.in
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+version https://git-lfs.github.com/spec/v1
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index 00000000..a2af386f
--- /dev/null
+++ b/LibreOJ/106/data/input3.out
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diff --git a/LibreOJ/106/data/input4.in b/LibreOJ/106/data/input4.in
new file mode 100644
index 00000000..df504c65
--- /dev/null
+++ b/LibreOJ/106/data/input4.in
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+version https://git-lfs.github.com/spec/v1
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index 00000000..51770412
--- /dev/null
+++ b/LibreOJ/106/data/input4.out
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diff --git a/LibreOJ/106/data/input5.in b/LibreOJ/106/data/input5.in
new file mode 100644
index 00000000..3dbba572
--- /dev/null
+++ b/LibreOJ/106/data/input5.in
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diff --git a/LibreOJ/106/data/input6.in b/LibreOJ/106/data/input6.in
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index 00000000..fb81dd88
--- /dev/null
+++ b/LibreOJ/106/data/input6.in
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+++ b/LibreOJ/106/data/input7.out
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diff --git a/LibreOJ/106/data/input8.in b/LibreOJ/106/data/input8.in
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diff --git a/LibreOJ/106/data/input9.in b/LibreOJ/106/data/input9.in
new file mode 100644
index 00000000..bc1c4124
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