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
import sys
sys.setrecursionlimit(2147483647)
INF=float("inf")
MOD=10**9+7
input=lambda:sys.stdin.readline().rstrip()

def max_rect_in_hist(Hist):
    Hist.append(0)
    ans=0
    Q=[(-1,0)]
    for i,h in enumerate(Hist):
        while(Q[-1][1]>h):
            i0,h0=Q.pop()
            ans=max(ans,h0*(i-Q[-1][0]-1))
        if(Q[-1][1]<=h):
            Q.append((i,h))
    return ans

def resolve():
    h,w=map(int,input().split())
    C=[list(map(lambda x:1-int(x),input().split())) for _ in range(h)]
    from itertools import product
    for i,j in product(range(h-1),range(w)):
        if(C[i+1][j]): C[i+1][j]+=C[i][j]
    print(max(max_rect_in_hist(c) for c in C))
resolve()
