Given a matrix (H × W) which contains only 1 and 0, find the area of the largest rectangle which only contains 0s.

Constraints

* 1 ≤ H, W ≤ 1,400

Input


H W
c1,1 c1,2 ... c1,W
c2,1 c2,2 ... c2,W
:
cH,1 cH,2 ... cH,W


In the first line, two integers H and W separated by a space character are given. In the following H lines, ci,j, elements of the H × W matrix, are given.

Output

Print the area (the number of 0s) of the largest rectangle.

Example

Input

4 5
0 0 1 0 0
1 0 0 0 0
0 0 0 1 0
0 0 0 1 0


Output

6
h, w = map(int, input().split())

mp = []
for _ in range(h):
  lst = list(map(int, input().split()))
  cum = []
  acc = 0
  for i in lst:
    if not i:
      acc += 1
    else:
      acc = 0
    cum.append(acc)
  mp.append(cum)
mp.append([-1] * w)
ans = 0

for i in range(w):
  stack = []

  for j in range(h + 1):
    score = mp[j][i]

    if not stack:
      stack.append((score, j))

    else:
      last_score, last_ind = stack[-1][0], stack[-1][1]
      if score > last_score:
        stack.append((score, j))
      
      elif score == last_score:
        continue
      
      else:
        while stack != [] and stack[-1][0] >= score:
          last_score, last_ind = stack.pop()
          ans = max(ans, last_score * (j - last_ind))
        stack.append((score, last_ind))

print(ans)
