#include <iostream>
using namespace std;

int s[1002][1002],i,j,n,d,sMax,su;
int main()
{
    cin>>n;
    for(i=1;i<=n;i++)
    for(j=1;j<=n;j++){
        cin>>s[i][j];
        s[i][j]=s[i][j]+s[i][j-1]+s[i-1][j]-s[i-1][j-1];
        d=1;
        while(i-d>=0&&j-d>=0){
            su=s[i][j]-s[i-d][j]-s[i][j-d]+s[i-d][j-d]-(s[i-1][j-1]-s[i+1-d][j-1]-s[i-1][j+1-d]+s[i+1-d][j+1-d]);
            if(su>sMax)sMax=su;
            d++;
        }
    }
    cout<<sMax;
    return 0;
}