別再一堆for或是while了

#include 

using namespace std;

int main(){
    int n, m, x1, y1, x2, y2, total[505][505];
    while (cin >> n >> m){
        for (int a = 1; a <= n; a++)
            for (int b = 1; b <= n; b++){
                cin >> total[a][b];
                total[a][b] += total[a - 1][b] + total[a][b - 1] - total[a - 1][b - 1];
            }
        while (m--){
            cin >> x1 >> y1 >> x2 >> y2;
            cout << total[x2][y2] - total[x1 - 1][y2] - total[x2][y1 - 1] + total[x1 - 1][y1 - 1] << endl;
        }
    }
    return 0;
}