diff --git a/S2OJ/100/100.cpp b/S2OJ/100/100.cpp
new file mode 100644
index 00000000..813c0a3e
--- /dev/null
+++ b/S2OJ/100/100.cpp
@@ -0,0 +1,105 @@
+#include <cstdlib>
+#include <iostream>
+
+using std::cin;
+using std::cout;
+#define endl '\n'
+
+const int N = 1e5 + 5;
+
+int n, m, l, r, root, cnt;
+
+struct node {
+    int l, r, s, v, k;
+    bool d;
+
+    node()
+        : l(0), r(0), s(0), v(0), d(false), k(rand()) {}
+    node(int _v)
+        : l(0), r(0), s(1), v(_v), d(false), k(rand()) {}
+} tr[N];
+
+void pushup(int u) {
+    tr[u].s = tr[tr[u].l].s + tr[tr[u].r].s + 1;
+}
+
+void pushdown(int u) {
+    if (tr[u].d) {
+        tr[u].d = false;
+        tr[tr[u].l].d ^= 1;
+        tr[tr[u].r].d ^= 1;
+        std::swap(tr[u].l, tr[u].r);
+    }
+}
+
+int build(int l, int r) {
+    if (l > r) return 0;
+    int mid = l + r >> 1;
+    int p = ++cnt;
+    tr[p] = node(mid - 1);
+    tr[p].l = build(l, mid - 1);
+    tr[p].r = build(mid + 1, r);
+    pushup(p);
+    return p;
+}
+
+std::pair<int, int> split(int p, int k) {
+    if (!p) return std::make_pair(0, 0);
+    pushdown(p);
+    if (k <= tr[tr[p].l].s) {
+        auto o = split(tr[p].l, k);
+        tr[p].l = o.second;
+        pushup(p);
+        o.second = p;
+        return o;
+    }
+    auto o = split(tr[p].r, k - tr[tr[p].l].s - 1);
+    tr[p].r = o.first;
+    pushup(p);
+    o.first = p;
+    return o;
+}
+
+int merge(int x, int y) {
+    if (!x || !y) return x | y;
+    pushdown(x);
+    pushdown(y);
+    if (tr[x].k > tr[y].k) {
+        tr[x].r = merge(tr[x].r, y);
+        pushup(x);
+        return x;
+    }
+    tr[y].l = merge(x, tr[y].l);
+    pushup(y);
+    return y;
+}
+
+void reserve(int l, int r) {
+    auto x = split(root, r + 1);
+    auto y = split(x.first, l);
+    tr[y.second].d ^= 1;
+    root = merge(merge(y.first, y.second), x.second);
+}
+
+void print(int p) {
+    if (!p) return;
+    pushdown(p);
+    print(tr[p].l);
+    if (1 <= tr[p].v && tr[p].v <= n) {
+        cout << tr[p].v << ' ';
+    }
+    print(tr[p].r);
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin >> n >> m;
+    root = build(1, n + 2);
+    while (m--) {
+        cin >> l >> r;
+        reserve(l, r);
+    }
+    print(root);
+    cout << endl;
+    return 0;
+}