H,W=map(int,input().split())
A=[]
B=[];C=[0]*W
D,E={},{}
for i in range(H):
  AA=list(map(int, input().split()))
  for j in range(W):
    C[j]+=AA[j]
    x=i+j
    if x not in D:
      D[x]=0
    y=i-j 
    if y not in E:
      E[y]=0
    D[x]+=AA[j];E[y]+=AA[j]
  A.append(AA)
  B.append(sum(AA))
if H==1 and W==1:
  print(AA[0])
  exit()
  
DD,EE=[],[]
for d in D:
  DD.append(D[d])
for e in E:
  EE.append(E[e])
BB=sorted(B)[::-1];CC=sorted(C)[::-1];DDD=sorted(DD)[::-1];EEE=sorted(EE)[::-1]
ans=0
if len(BB)>1:
  ans=max(ans,BB[0]+BB[1])
if len(CC)>1:
  ans=max(ans,CC[0]+CC[1])
if len(DD)>1:
  ans=max(ans,DDD[0]+DDD[1])
if len(EE)>1:
  ans=max(ans,EEE[0]+EEE[1])
  
for d in D:
  for e in E:
    if (d+e)%2==0 and (d-e)%2==0:
      x,y=(d+e)//2,(d-e)//2
      if 0<=x<H and 0<=y<W:
        f=1
      else:
        ans=max(ans,D[d]+E[e])

for h in range(H):
  for w in range(W):
    a=A[h][w]
    CC=[B[h],C[w],D[h+w],E[h-w]]
    CC=sorted(CC)[::-1]
    ans=max(ans,CC[0]+CC[1]-a)
print(ans)