H, W = map(int, input().split())
A = []
for i in range(H):
    A.append(list(map(int, input().split())))
    
L = []
for i in range(H):
    for j in range(W):
        if i == 0 or i == H - 1 or j == 0 or j == W - 1:
            L.append((i, j))
            
dx = [1, 0, 1, 1]
dy = [0, 1, 1, -1]

def f(x1, y1, k1, x2, y2, k2):
    S = set()
    while True:
        S.add((x1, y1))
        x1 += dx[k1]
        y1 += dy[k1]
        if x1 < 0 or x1 > H - 1 or y1 < 0 or y1 > W - 1:
            break
    while True:
        S.add((x2, y2))
        x2 += dx[k2]
        y2 += dy[k2]
        if x2 < 0 or x2 > H - 1 or y2 < 0 or y2 > W - 1:
            break
    return S

ans = 0
for x1, y1 in L:
    for k1 in range(4):
        for x2, y2 in L:
            for k2 in range(4):
                S = f(x1, y1, k1, x2, y2, k2)
                temp = 0
                for xs, ys in S:
                    temp += A[xs][ys]
                ans = max(ans, temp)
                
print(ans)