diff --git a/Luogu/P3396/P3396.cpp b/Luogu/P3396/P3396.cpp
new file mode 100644
index 00000000..9b2aa894
--- /dev/null
+++ b/Luogu/P3396/P3396.cpp
@@ -0,0 +1,53 @@
+#include <cmath>
+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1.5e5 + 5,
+          NS = 505;
+
+int n, m, t, a[N], f[NS][NS];
+char op;
+
+int main() {
+    std::ios::sync_with_stdio(false);
+
+    cin >> n >> m;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> a[i];
+    }
+
+    t = std::ceil(std::sqrt(n));
+
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= t; j++) {
+            f[j][i % j] += a[i];
+        }
+    }
+
+    for (int i = 1, x, y; i <= m; i++) {
+        cin >> op >> x >> y;
+
+        if (op == 'A') {
+            if (x <= t) {
+                cout << f[x][y % x] << endl;
+            } else {
+                int ans = 0;
+                for (int i = y; i <= n; i += x) {
+                    ans += a[i];
+                }
+                cout << ans << endl;
+            }
+        } else {  // op == 'C'
+            for (int j = 1; j <= t; j++) {
+                f[j][x % j] += (y - a[x]);
+            }
+            a[x] = y;
+        }
+    }
+
+    return 0;
+}