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, collections

def solve():
    file_input = sys.stdin
    H, W = map(int, file_input.readline().split())
    max_area = 0
    prev = [0] * W
    rect_stack = collections.deque()
    for line in file_input:
        tile_line = map(int, line.split())
        for i, tpl in enumerate(zip(tile_line, prev)):
            t, p = tpl
            if t:
                h = 0
                prev[i] = 0
            else:
                h = p + 1
                prev[i] = h
            if (not rect_stack) or (h > rect_stack[-1][0]):
                rect_stack.append((h, i))
            elif h < rect_stack[-1][0]:
                while rect_stack:
                    if rect_stack[-1][0] >= h:
                        rect_h, rect_i = rect_stack.pop()
                        max_area = max(max_area, rect_h * (i - rect_i))
                    else:
                        break
                rect_stack.append((h, rect_i))
        while rect_stack:
            rect_h, rect_i = rect_stack.pop()
            max_area = max(max_area, rect_h * (W - rect_i))
    print(max_area)

solve()