Forest density

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

int main() {
    int n, q;
    cin >> n >> q;
    vector<vector<char>> grid(n);

    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            char t;
            cin >> t;
            grid[i].push_back(t);
        }
    }

    vector<vector<int>> query(q);
    for (int i = 0; i < q; i++) {
        for (int j = 0; j < 4; j++) {
            int t;
            cin >> t;
            query[i].push_back(t - 1);
        }
    }

    vector<vector<int>> sum(n);
    for (int i = 0; i < n; i++) {
        int curr = 0;
        for (int j = 0; j < n; j++) {
            int last;
            if (i == 0) last = 0;
            else last = sum[i - 1][j];
            if (grid[i][j] == '*') curr++;
            sum[i].push_back(curr + last);
        }
    }

    for (int i = 0; i < q; i++) {
        int ans = sum[query[i][2]][query[i][3]] - sum[query[i][2]][query[i][1]] - sum[query[i][0]][query[i][3]] + sum[query[i][0]][query[i][1]];
        cout << ans << '\n';
    }



}

Test 1

Verdict: WRONG ANSWER

Test 2

Verdict: WRONG ANSWER

Test 3

Verdict: WRONG ANSWER