H, W = map(int, input().split())
W = 2 * H + W - 2
A = [[0] * (H - 1) + list(map(int, input().split())) + [0] * (H - 1) for _ in range(H)]
N = W * 3 + H
D = [(1, -1), (1, 0), (1, 1), (0, 1)]
S = [0] * N
for i in range(N):
    if i < W * 3:
        y = i // 3
        x = 0
        d = i % 3
    else:
        y = 0
        x = i - W * 3
        d = 3
    tmp = 0
    while 0 <= x < H and 0 <= y < W:
        tmp += A[x][y]
        x += D[d][0]
        y += D[d][1]
    S[i] = tmp
#for i in range(H):
    #print(*A[i])
#print(S)
ans = 0
for i in range(N - 1):
    if i < W * 3:
        y1 = i // 3
        x1 = 0
        d1 = i % 3
    else:
        y1 = 0
        x1 = i - W * 3
        d1 = 3
    for j in range(i + 1, N):
        tmp = S[i] + S[j]
        if j < W * 3:
            y2 = j // 3
            x2 = 0
            d2 = j % 3
        else:
            x2 = j - W * 3
            y2 = 0
            d2 = 3
        if d2 == 3:
            if d1 == 0:
                if 0 <= y1 - x2 < W:
                    tmp -= A[x2][y1 - x2]
            elif d1 == 1:
                tmp -= A[x2][y1]
            elif d1 == 2:
                if 0 <= y1 + x2 < W:
                    tmp -= A[x2][y1 + x2]
            ans = max(ans, tmp)
            #print(i,j,":","a",x1,y1,d1,x2,y2,d2,":",S[i]+S[j],tmp)
            continue
        if y1 == y2:
            tmp -= A[0][y1]
            #print(i,j,":","b",x1,y1,d1,x2,y2,d2,":",S[i]+S[j],tmp)
            ans = max(ans, tmp)
            continue
        if d2 == 0:
            if d1 == 2:
                yt = y2 - y1
                if yt % 2 == 0 and yt // 2 < H:
                    tmp -= A[yt // 2][(y2 + y1) // 2]
            elif d1 == 1:
                if y2 - y1 < H:
                    tmp -= A[y2 - y1][y1]
            #print(i,j,":","c",x1,y1,d1,x2,y2,d2,":",S[i]+S[j],tmp)
            ans = max(ans, tmp)
            continue
        if d2 == 1 and d1 == 2:
            if y2 - y1 < H:
                tmp -= A[y2 - y1][y2]
                #print(i, j, ":","d", x1, y1, d1, x2, y2, d2, ":", S[i] + S[j], tmp)
                ans = max(ans, tmp)
                continue
        #print(i, j, ":","e", x1, y1, d1, x2, y2, d2, ":", S[i] + S[j], tmp)
        ans = max(ans, tmp)
print(ans)