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())
height = W * [0]
max_area = 0
for _ in range(H):
    height = [0 if t else height[j]+1 for j, t in enumerate(map(int, input().split()))]
    height.append(0)
    stack = []
    for i, h in enumerate(height):
        if stack:
            if stack[-1][1] == h:
                continue
            elif stack[-1][1] > h:
                while stack and (stack[-1][1] >= h):
                    i_stack, h_stack = stack.pop()
                    max_area = max(max_area, (i - i_stack) * (h_stack))
                i = i_stack
                
            
        stack.append((i, h))
        
print(max_area)
