Ruudukko

#include <bits/stdc++.h>
#define F first
#define S second
#define X real()
#define Y imag()
using namespace std;
typedef long double ld;
typedef long long ll;

const ll mod=1e9+7;

ll a[1010][1010];

int main(){
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	ll n;
	cin>>n;
	ll ans=0;
	for (ll i=0;i<n;i++){
		for (ll ii=0;ii<n;ii++){
			cin>>a[i][ii];
			ll x=(i+1ll)*(ii+1ll);
			ll y=(n-i)*(n-ii);
			ans+=((x*y)%mod)*a[i][ii];
			ans%=mod;
		}
	}
	cout<<ans<<endl;
}

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 2, 3

Verdict: ACCEPTED

Test 3

Group: 3

Verdict: ACCEPTED