Ruudukko

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

int n;
ll a[1010][1010];
ll M = 1000000007LL;

int main() {
  ios_base::sync_with_stdio(0); cin.tie(0);
  cin>>n;

  for (int y = 0; y < n; y++) {
    for (int x = 0; x < n; x++) {
      cin>>a[y][x];
    }
  }

  ll ans = 0;

  for (int y = 0; y < n; y++) {
    for (int x = 0; x < n; x++) {
      ll add = (y+1LL) * (x+1LL);
      add %= M;
      add *= ll(n) - ll(x);
      add %= M;
      add *= ll(n) - ll(y);
      add %= M;
      add *= a[y][x];
      add %= M;
      ans += add;
      ans %= M;
    }
  }

  if (ans < 0LL) ans += M;
  cout << ans << "\n";
}

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 2, 3

Verdict: ACCEPTED

Test 3

Group: 3

Verdict: ACCEPTED