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

def resolve():
    def get_largest_rectangle(hist: list):
        hist = hist.copy()
        hist.append(0)
        ret = 0
        stack = []
        for i, v in enumerate(hist):
            if len(stack) == 0:
                stack.append((i, v))
            elif stack[-1][1] < v:
                stack.append((i, v))
            elif stack[-1][1] > v:
                while stack and stack[-1][1] > v:
                    i_left, h = stack.pop()
                    ret = max(ret, (i - i_left)*h)
                stack.append((i_left, v))
        return ret


    H, W = map(int, input().split())
    AB = [list(map(int, input().split())) for _ in range(H)]
    T = [[0]*W for _ in range(H)]

    for j in range(W):
        seq = 0
        for i in range(H):
            if AB[i][j] == 1:
                T[i][j] = 0
                seq = 0
            else:
                T[i][j] = seq + 1
                seq += 1
    ans = 0
    for t in T:
        ans = max(ans, get_largest_rectangle(t))
    print(ans)

if __name__ == '__main__':
    resolve()
