diff --git a/problem/P1531/P1531.cpp b/problem/P1531/P1531.cpp
new file mode 100644
index 00000000..a1886185
--- /dev/null
+++ b/problem/P1531/P1531.cpp
@@ -0,0 +1,84 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+struct node {
+    int l, r;
+    int max;
+
+    node() {
+        l = r = 0;
+        max = -0x3f3f3f3f;
+    }
+    node(int _l, int _r) {
+        l = _l;
+        r = _r;
+        max = -0x3f3f3f3f;
+    }
+} tr[200005 << 2];
+int n, m, x, y, a[200005];
+char op;
+
+void pushup(int u) {
+    tr[u].max = max(tr[u << 1].max, tr[u << 1 | 1].max);
+}
+
+void build(int u, int l, int r) {
+    tr[u] = node(l, r);
+    if (l == r) {
+        tr[u].max = a[l];
+        return;
+    }
+    int mid = l + r >> 1;
+    build(u << 1, l, mid);
+    build(u << 1 | 1, mid + 1, r);
+    pushup(u);
+}
+
+void modify(int u, int x, int d) {
+    if (tr[u].l == x && tr[u].r == x) {
+        tr[u].max = max(tr[u].max, d);
+        return;
+    }
+    int mid = tr[u].l + tr[u].r >> 1;
+    if (x <= mid) {
+        modify(u << 1, x, d);
+    }
+    else {
+        modify(u << 1 | 1, x, d);
+    }
+    pushup(u);
+}
+
+int query(int u, int l, int r) {
+    if (tr[u].l >= l && tr[u].r <= r) {
+        return tr[u].max;
+    }
+    int mid = tr[u].l + tr[u].r >> 1;
+    int v = 0;
+    if (l <= mid) {
+        v = query(u << 1, l, r);
+    }
+    if (r > mid) {
+        v = max(v, query(u << 1 | 1, l, r));
+    }
+    return v;
+}
+
+int main() {
+    cin >> n >> m;
+    for (int i = 1; i <= n; i++) {
+        cin >> a[i];
+    }
+    build(1, 1, n);
+    while (m--) {
+        cin >> op >> x >> y;
+        if (op == 'U') {
+            modify(1, x, y);
+        }
+        else if (op == 'Q') {
+            cout << query(1, x, y) << endl;
+        }
+    }
+    return 0;
+}