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
#include <algorithm>
#include <cstdio>
#include <iostream>
#include <stack>

using namespace std;

struct elem {
	int pos, height;
};

int getArea(int V[], int W) {
	int area = 0;
	stack<elem> S;
	for (int i = 0; i <= W; ++i) {
		elem e;
		e.pos = i;
		if (i == W) {
			e.height = 0;
		} else {
			e.height = V[i];
		}
		if (S.empty() || e.height > S.top().height) {
			S.push(e);
		} else {
			int prepos = i;
			while (!S.empty() && S.top().height > e.height) {
				elem target = S.top();
				S.pop();
				area = max(area, (i - target.pos) * target.height);
				prepos = target.pos;
			}
			e.pos = prepos;
			S.push(e);
		}
	}
	return area;
}
int main() {
	int H, W;
	scanf("%d %d", &H, &W);
	int A[H][W];
	for (int i = 0; i < H; ++i) {
		for (int j = 0; j < W; ++j) {
			scanf("%d", &A[i][j]);
		}
	}

	int V[H][W];
	for (int j = 0; j < W; ++j) {
		for (int i = 0; i < H; ++i) {
			if (A[i][j] == 1) {
				V[i][j] = 0;
			} else {
				if (i == 0) {
					V[i][j] = 1;
				} else {
					V[i][j] = V[i - 1][j] + 1;
				}
			}
		}
	}

	int maxv = 0;
	for (int i = 0; i < H; ++i) {
		maxv = max(maxv, getArea(V[i], W));
	}
	cout << maxv << endl;

	return 0;
}