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())
max_rect, prev = 0, [0] * (w + 1)
for i in range(h):
    current = [p + 1 if f else 0 for f, p in zip(map(lambda x: int(x) ^ 1, input().split()), prev)] + [0]
    stack = [(0, 0)]
    for j in range(w + 1):
        c_j = current[j]
        if stack[-1][0] < c_j:
            stack.append((c_j, j))
            continue
        if stack[-1][0] > c_j:
            since = 0
            while stack[-1][0] > c_j:
                height, since = stack.pop()
                max_rect = max(max_rect, height * (j - since))
            if c_j:
                stack.append((c_j, since))
    prev = current
print(max_rect)