Ruudukko

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

#ifdef LOCAL
#define D(x) {x;}
#else
#define D(x)
#endif
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()

using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;

const ll M = 1e9+7;

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cin.exceptions(cin.failbit);
    int n;
    cin >> n;
    ll res = 0;
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            ll a;
            cin >> a;
            res += a * ll(i + 1) * (j + 1) %M * (n-i) * (n-j) % M;
            res %= M;
        }
    }
    cout << res << endl;
}

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 2, 3

Verdict: ACCEPTED

Test 3

Group: 3

Verdict: ACCEPTED