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
from collections import deque

def rectangle(n, hs): #n:?¨????hs: ???????????°??????
    stack = deque() # stack = (j, h) ????????¨?????????????´??????????
    ans = 0
    for i, h in enumerate(hs):
        j = -1
        while stack and stack[-1][1] > h:
            j, h2 = stack.pop()
            ans = max(ans, (i-j) * h2)
            
        if not stack or stack[-1][1] < h: #stack?????????????????????stack?????????????????????"??????h"?????????????????°?????????????????????????°????????????°???????£???¨??????stack????????????
            stack.append( (i if j == -1 else j, h))
        
    ans = max(ans, max((n-j) * h2 for j, h2 in stack))
    
    return ans
    
H, W = map(int, input().split())
hs = [0] * W
result = 0

for i in range(H):
    ht = list(map(int, input().split()))
    hs = list(map(lambda x, y: (x+1) * abs(y-1), hs, ht)) #???????????°???????????????
    result = max(result, rectangle(W, hs))
    
print(result)