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<iostream>
#include<algorithm>
using namespace std;

#define MAX_N 2000
int x[MAX_N][MAX_N];
int H, W;
int main() {
	cin >> H >> W;
	for (int i = 0; i < H; i++) {
		for (int j = 0; j < W; j++) {
			cin >> x[i][j];
		}
		if (x[i][0] == 1) { x[i][0] = 0; }
		else { x[i][0] = 1; }
		for (int j = 1; j < W; j++) {
			if (x[i][j] == 1) {
				x[i][j] = 0;
			}
			else {
				x[i][j] = x[i][j - 1] + 1;
			}
		}
	}
	int maxn = 0;
	for (int i = 0; i < W; i++) {
		for (int j = 0; j < H; j++) {
			int X = x[j][i], cnt = 0;
			if (x[j][i] == 0)continue;
			for (int k = j; k >= 0; k--) {
				cnt++; X = min(X, x[k][i]);
				if (X*(j + 1) <= maxn) { break; }
				maxn = max(maxn, X*cnt);
			}
		}
	}
	cout << maxn << endl;
	return 0;
}