#include <stdio.h>

#define NMAX 55
#define INF 1000000000

int A[NMAX][NMAX], SA[NMAX][NMAX], ans;
int N, i, j, rup, rdown, cleft, cright, sum, csum;

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

	for (j = 1; j <= N; j++) {
		SA[0][j] = 0;
		for (i = 1; i <= N; i++)
			SA[i][j] = SA[i - 1][j] + A[i][j];
	}

	ans = -INF;
	for (rup = 1; rup <= N; rup++)
		for (rdown = rup; rdown <= N; rdown++)
			for (cleft = 1; cleft <= N; cleft++) {
				sum = SA[rdown][cleft] - SA[rup - 1][cleft];
				if (sum > ans && rup == rdown)
					ans = sum;

				for (cright = cleft + 1; cright <= N; cright++) {
					csum = sum + SA[rdown][cright] - SA[rup - 1][cright];
					if (csum > ans && (rdown - rup == cright - cleft))
						ans = csum;

					sum += A[rup][cright];
					if (rdown > rup)
						sum += A[rdown][cright];
				}
			}


	printf("%d\n", ans);
	return 0;
}