h,w=map(int,input().split())
a=[list(map(int,input().split())) for i in range(h)]
if h<=2 or w<=2:
  g=0
  for i in range(h):
    for j in range(w):
      g+=a[i][j]
  print(g)
  exit()
g=0
for kaiten in range(4):
  for hanten in range(2):
    A=[[0]*(h-1+w+h-1) for i in range(h)]
    for i in range(h):
      for j in range(w):
        A[i][j+h-1]=a[i][j]
    b1=[[0]*(h-1+w+h-1) for i in range(h)]
    for i in range(h):
      b1[i][h-1+w-1+i]=sum(A[i])
    for i in range(h):
      for j in reversed(range(i,i+h-1+w-1)):
        b1[i][j]=b1[i][j+1]
    b2=[[0]*(h-1+w+h-1) for i in range(h)]
    for j in range(h-1,h-1+w+h-1):
      b2[h-1][j]=sum(A[h-1-i][j-i] for i in range(h))
    for i in reversed(range(h-1)):
      for j in range(i,i+w+h-1):
        b2[i][j]=b2[i+1][j+1]
    g=max(g,sum((sorted([b1[i][h-1+w-1+i] for i in range(h)]))[::-1][:2]))
    g=max(g,sum((sorted([b2[h-1][h-1+i] for i in range(h+w-1)]))[::-1][:2]))
    for i in range(h):
      for j in range(i,i+h-1+w):
        g=max(g,b1[i][j]+b2[i][j]-A[i][j])
    na=[[0]*w for i in range(h)]
    for i in range(h):
      for j in range(w):
        na[i][~j]=a[i][j]
    a=na
  na=[[0]*h for i in range(w)]
  for i in range(h):
    for j in range(w):
      na[~j][i]=a[i][j]
  h,w=w,h
  a=na
print(g)