• 直接按照题意模拟
• 时间复杂度：$O(nm)$，会 TLE

#include <bits/stdc++.h>
using namespace std;

using i64 = long long;

int main() {	
    ios::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    
    int n, m;
    cin >> n >> m;
    vector<int> a(n + 1);
    for (int i = 1; i <= n; i++) cin >> a[i];
    
    string cmd;
    int x, y;
    while (m--) {
        cin >> cmd >> x >> y;
        if (cmd == "A") {
            i64 ans = 0;
            for (int i = y; i <= n; i += x) ans += a[i];
            cout << ans << '\n';
        } else {
            a[x] = y;
        }
    }
    return 0;
}