#include <cstdio>
#define Nmax 56

using namespace std;

int a[Nmax][Nmax], N, sumL[Nmax][Nmax], sumC[Nmax][Nmax];

int main(){

    //freopen("fis.in", "r", stdin);

    scanf("%d", &N);

    for(int i = 1; i <= N; ++i){
        for(int j = 1; j <= N; ++j){
            scanf("%d", &a[i][j]);
        }
    }

    //Sum linie
    for(int i = 1; i <= N; ++i){
        for(int j = 1; j <= N; ++j){
            sumL[i][j] = sumL[i][j-1] + a[i][j];
        }
    }
    

    //Sum coloana
    for(int j = 1; j <= N; ++j){
        for(int i = 1; i <= N; ++i){
            sumC[i][j] = sumL[i-1][j] + a[i][j];
        }
    }

    //Corner
    int sol = -51*51*100;
    for(int i = 1; i <= N; ++i){
        for(int j = 1; j <= N; ++j)
            for(int len = 1; len <= i && len <= j; ++len){
                int c = 0;

                if(len > 1){
                    c= sumL[i][j] - sumL[i-len][j] +
                        sumC[i][j] - sumL[i][j-len];
                    c += sumL[i - len + 1][j] - sumL[i - len + 1][j - len];
                    c += sumC[i][j - len + 1] - sumC[i - len][j-len + 1];

                    c -= a[i][j] + a[i-len + 1][j]  + a[i-len+1][j-len+1];
                }

                else {
                    c = a[i][j];
                }

                if(c > sol )
                    sol = c;
                        
            }
    }

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

    return 0;
}