#include
#includeusingnamespace std;
constint nil=-(1<<29);
constint maxn=100;
int sum[maxn][maxn];
int main(){
int n;
scanf("%d",&n);
int p;
for (int i=1;i<=n;i++){
for (int j=1;j<=n;j++){
scanf("%d",&p);
sum[i][j]=sum[i][j-1]+p;
}
}
int ans=nil;
for (int i=1;i<=n;i++){
for (int j=i;j<=n;j++){
int num=0;
for (int k=1;k<=n;k++){
if(num<0) num=0;
num+=sum[k][j]-sum[k][i-1];
ans=max(ans,num);
}
}
}
printf("%d\n",ans);
return0;
}