class Max2:
  def __init__(self,
  fst_key=-1, fst_val=-9*10**18,
  snd_key=-2, snd_val=-9*10**18):
    self.fst_key, self.fst_val = fst_key, fst_val
    self.snd_key, self.snd_val = snd_key, snd_val
  def chmax2(self, key, val):
    if key == self.fst_key:
      self.fst_val = max(self.fst_val, val)
    elif val > self.fst_val:
      self.snd_key, self.snd_val = self.fst_key, self.fst_val
      self.fst_key, self.fst_val = key, val
    elif val > self.snd_val:
      self.snd_key, self.snd_val = key, val


from itertools import product

H, W = map(int, input().split())
A = [[0]*(2*H+W) for _ in range(2*W+H)]
for i in range(H):
  A[W+i][H:H+W] = list(map(int, input().split()))

row, col = [0]*(2*W+H), [0]*(2*H+W)
diag, skew = [0]*(3*H+3*W), [0]*(3*H+3*W)
for i, j in product(range(2*W+H), range(2*H+W)):
  row[i] += A[i][j]; col[j] += A[i][j]
  diag[i-j] += A[i][j]; skew[i+j] += A[i][j]

row_max2, col_max2 = Max2(), Max2()
diag_max2, skew_max2 = Max2(), Max2()
for i in range(2*W+H): row_max2.chmax2(i, row[i])
for j in range(2*H+W): col_max2.chmax2(j, col[j])
for k in range(3*H+3*W): diag_max2.chmax2(k, diag[k])
for l in range(3*H+3*W): skew_max2.chmax2(l, skew[l])

ans = max(
  row_max2.fst_val + row_max2.snd_val,
  col_max2.fst_val + col_max2.snd_val,
  diag_max2.fst_val + diag_max2.snd_val,
  skew_max2.fst_val + skew_max2.snd_val
)
for i, j in product(range(2*W+H), range(2*H+W)):
  max2 = Max2(0, row[i]); max2.chmax2(1, col[j])
  max2.chmax2(2, diag[i-j]); max2.chmax2(3, skew[i+j])
  ans = max(ans, max2.fst_val + max2.snd_val - A[i][j])

even_diag_max = odd_diag_max = 0
even_skew_max = odd_skew_max = 0
for k in range(3*H+3*W):
  if k%2: odd_diag_max = max(odd_diag_max, diag[k])
  else: even_diag_max = max(even_diag_max, diag[k])
for l in range(3*H+3*W):
  if l%2: odd_skew_max = max(odd_skew_max, skew[l])
  else: even_skew_max = max(even_skew_max, skew[l])

ans = max(ans,
  even_diag_max + odd_skew_max,
  even_skew_max + odd_diag_max
)
print(ans)