"""
作者：LYY
日期：2023年 09月 16日 14时 38分
"""
import numpy as np


def main():
    n, m = map(np.long, input().split(" "))
    data = np.zeros((n, m), dtype=np.long)
    for i in range(n):
        data[i] = list(map(np.long, input().split(" ")))
    ans = np.zeros((n + 1, m + 1, n + 1, m + 1), dtype=np.long)
    for i in range(1, n + 1):
        for j in range(1, m + 1):
            for ii in range(1, n + 1):
                for jj in range(1, m + 1):
                    if i < ii and j > jj:
                        ans[i][j][ii][jj] = max(ans[i - 1][j][ii - 1][jj], ans[i - 1][j][ii][jj - 1],
                                                ans[i][j - 1][ii - 1][jj],
                                                ans[i][j - 1][ii][jj - 1]) + data[i - 1][j - 1] + data[ii - 1][jj - 1]
    print(max(ans[n - 1][m][n - 1][m], ans[n - 1][m][n][m - 1], ans[n][m - 1][n - 1][m], ans[n][m - 1][n][m - 1]),
          end="")


if __name__ == "__main__":
    main()