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 sys import stdin
readline = stdin.readline


h, w = map(int, readline().split())
w += 1
dp = [list(map(int, readline().split())) + [1] for _ in range(h)]

for i in range(h):
    for j in range(w):
        dp[i][j] ^= 1
    
for i in range(1, h):
    for j in range(w):
        if dp[i][j]:
            dp[i][j] += dp[i - 1][j]

max_s = 0
for i in range(h):
    stack = []
    for j in range(w):
        if (stack[-1][0] if stack else 0) < dp[i][j]:
            stack.append((dp[i][j], j))
        elif stack and stack[-1][0] > dp[i][j]:
            while stack and stack[-1][0] > dp[i][j]:
                height, l = stack.pop()
                s = height * (j - l)
                if max_s < s:
                    max_s = s
            if dp[i][j]:
                stack.append((dp[i][j], l))
print(max_s)