h,w = map(int,input().split())
a = [[0]*(w+3)]+[[0]+list(map(int,input().split()))+[0,0] for _ in range(h)]+[[0]*(w+3),[0]*(w+3)]
s = []; ans = 0
for x in range(h+2):
    for dx in range(-1,2):
        px = x+dx; py = 1; t = set(); u = 0
        while a[px][py]: t.add((px,py)); u += a[px][py]; px += dx; py += 1
        s.append((u,t))
for y in range(w+2):
    for dy in range(-1,2):
        px = 1; py = y+dy; t = set(); u = 0
        while a[px][py]: t.add((px,py)); u += a[px][py]; px += 1; py += dy
        s.append((u,t))
for x in range(h+2):
    dx = 1; px = x+dx; py = w; t = set(); u = 0
    while a[px][py]: t.add((px,py)); u += a[px][py]; px += dx; py -= 1
    s.append((u,t))
for y in range(w+2):
    dy = 1; px = h; py = y+dy; t = set(); u = 0
    while a[px][py]: t.add((px,py)); u += a[px][py]; px -= 1; py += dy
    s.append((u,t))
s.sort(reverse=True)
for i in range(len(s)-1):
    for j in range(i+1,len(s)):
        if s[i][0]+s[j][0]<ans: break
        ans = max(ans,sum(a[x][y] for x,y in s[i][1]|s[j][1]))
print(ans)