#include<cstdio>
using namespace std;
int x,n,maxi,i,i1,i2,j,j1,j2,a[59][59],s[59][59];
int sum(int i1,int j1,int i2,int j2)
{
    if(i1>i2||j1>j2) return 0;
    return s[i2][j2]-s[i1-1][j2]-s[i2][j1-1]+s[i1-1][j1-1];
}
int main()
{
//freopen("input","r",stdin);
//freopen("output","w",stdout);
maxi=-100000000;
scanf("%d",&n);
for(i=1;i<=n;i++)
    for(j=1;j<=n;j++)
    {
        scanf("%d",&a[i][j]);
        s[i][j]=s[i-1][j]+s[i][j-1]-s[i-1][j-1]+a[i][j];
    }
for(i1=1;i1<=n;i1++)
    for(i2=i1;i2<=n;i2++)
        for(j1=1;j1<=n;j1++)
            for(j2=j1;j2<=n;j2++)
            {
                if(i1==1&&j1==3&&i2==1&&j2==3)
                    s[0][0]=0;
                if(i1<i2&&j1<j2) x=sum(i1,j1,i2,j2)-sum(i1+1,j1+1,i2-1,j2-1);
                else x=sum(i1,j1,i2,j2);
                if(x>maxi)
                    maxi=x;
            }
printf("%d\n",maxi);
return 0;
}