#include <bits/stdc++.h>

using namespace std;

const int N = 1e3 + 5;

int n, a[N][N], dp[4][N][N];
int ans = -2e9;

int max_item_sum(vector <vector <int>> V){
    n = V.size();
    for (int i = 1; i <= n; ++ i) for (int j = 1; j <= n; ++ j) a[i][j] = V[i - 1][j - 1];

    for (int i = 1; i <= n; ++ i){
        for (int j = n; j >= 1; -- j){
            dp[1][i][j] = max(dp[1][i - 1][j], dp[1][i][j + 1]) + a[i][j];
        }
    }

    for (int i = n; i >= 1; -- i){
        for (int j = 1; j <= n; ++ j){
            dp[2][i][j] = max(dp[2][i + 1][j], dp[2][i][j - 1]) + a[i][j];
        }
    }

    for (int i = 1; i <= n; ++ i){
        for (int j = 1; j <= n; ++ j){
            dp[0][i][j] = max(dp[0][i][j - 1], dp[0][i - 1][j]) + a[i][j];
         }
    }

    for (int i = n; i >= 1; -- i){
        for (int j = n; j >= 1; -- j){
            dp[3][i][j] = max(dp[3][i + 1][j], dp[3][i][j + 1]) + a[i][j];
        }
    }

    for (int i = 1; i <= n; ++ i){
        int pre = -2e9;
        for (int j = 1; j <= n; ++ j){
            pre = max(pre, dp[0][i - 1][j] + dp[2][i + 1][j]) + a[i][j];
            ans = max(ans, pre + dp[1][i - 1][j] + dp[3][i + 1][j]);
        }
    }

    for (int j = 1; j <= n; ++ j){
        int pre = -2e9;
        for (int i = 1; i <= n; ++ i){
            pre = max(pre, dp[0][i][j - 1] + dp[1][i][j + 1]) + a[i][j];
            ans = max(ans, pre + dp[2][i][j - 1] + dp[3][i][j + 1]);
        }
    }

    //for (int i = 0; i < 4; ++ i) cout << dp[i][3][2] << endl;

    return ans;
}

//void my_assert (bool x) {
//	if (!x) {
//		puts("Wrong input");
//		exit(0);
//	}
//}
//
//int main() {
//	int N;
//	my_assert(scanf("%d", &N) == 1);
//
//	std::vector<std::vector<int>> V(N, std::vector<int>(N));
//	for (int i = 0; i < N; i++) {
//		for (int j = 0; j < N; j++) {
//			my_assert(scanf("%d", &V[i][j]) == 1);
//		}
//	}
//
//	int ans = max_item_sum(V);
//	printf("%d\n", ans);
//
//	return 0;
//}