import java.util.*;

public class Main {
    static final int N = 53;
    static int[][] g = new int[N][N];
    static int[][][] f = new int[2 * N][N][N];
    static int n, m;

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        String[] s1 = sc.nextLine().split(" ");
        n = Integer.parseInt(s1[0]); m = Integer.parseInt(s1[1]);

        for (int i = 1; i <= n; i++) {
            String[] s2 = sc.nextLine().split(" ");
            g[i] = toIntArr(s2);
        }        

        int ans = dp();

        System.out.println(ans);
    }

    static int dp() {
        for (int k = 2; k <= n + m; k ++ )
        for (int i = Math.max(1, k - m); i <= n && i < k; i ++ )
            for (int j = Math.max(1, k - m); j <= n && j < k; j ++ )
                for (int a = 0; a <= 1; a ++ )
                    for (int b = 0; b <= 1; b ++ )
                    {
                        int t = g[i][k - i];
                        if (i != j || k == 2 || k == n + m)
                        {
                            t += g[j][k - j];
                            f[k][i][j] = Math.max(f[k][i][j], f[k - 1][i - a][j - b] + t);
                        }
                    }

        return f[m + n][n][n];
    }

    static int[] toIntArr(String[] str) {
        int[] res = new int[str.length + 1];
        for (int i = 1; i <= str.length; i++) res[i] = Integer.parseInt(str[i - 1]);
        return res;
    }
}