Given an N*N matrix, find the coolest square sub-matrix.
We define the cool value of the square matrix as X-Y where X indicating the sum of all integers of the main diagonal and Y indicating the sum of the other diagonal.

The first line has a positive integer N (2 ≤ N ≤ 400), the size of the matrix.
The following N lines each contain N integers in the range [-1000, 1000], the elements of the matrix.

Output the coolest value of a square sub-matrix.

#include <stdio.h>

#include <algorithm>

using namespace std;

int a[][],b[][];

int main(){

    int n;

    scanf("%d",&n);

    for(int i=;i<=n;i++)

    for(int j=;j<=n;j++){

        int x;

        scanf("%d",&x);

        a[i][j]=x+a[i-][j-];b[i][j]=x+b[i-][j+];

    }

    int ma=;

    for(int i=;i<=n;i++)

    for(int j=;j<=n;j++)

    for(int k=;k<=i&&k<=j;k++)

    ma=max(ma,a[i][j]-a[i-k][j-k]-b[i][j-k+]+b[i-k][j+]);

    printf("%d\n",ma);

    return ;

}