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())
c = [list(map(int,input().split())) for _ in range(h)]

T = [[0]*(w+1) for _ in range(h)]

for j in range(w):
    for i in range(h):
        if c[i][j] == 1:
            continue
        else:
            T[i][j] = T[i-1][j]+1 if i>0 else 1
            
maxv = 0
for i in range(h):
    S = []
    
    for j in range(w+1):
        rect = [T[i][j],j]
        if S:
            if S[-1][0]<rect[0]:
                S.append(rect)
            elif S[-1][0]>rect[0]:
                target = j
                while(S and S[-1][0]>=rect[0]):
                    pre = S.pop()
                    area = pre[0]*(j-pre[1])
                    maxv = max(maxv,area)
                    target = pre[1]
                rect[1] = target
                S.append(rect)
        else:
            S.append(rect)
            
print(maxv)
