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<stdio.h>
#include<iostream>
#include<stack>
#include<algorithm>
#define MAX 1400

using namespace std;

struct Rectangle{int height; int pos;};

int getLargestRectangle(int size, int buffer[]){
	stack<Rectangle> S;
	int maxv = 0;
	buffer[size] = 0;

	for(int i = 0; i <= size; i++){
		Rectangle rect;
		rect.height = buffer[i];
		rect.pos = i;
		if(S.empty()){
			S.push(rect);
		}else{
			if(S.top().height < rect.height){
				S.push(rect);
			}else if(S.top().height > rect.height){
				int target = i;
				while(!S.empty() && S.top().height >= rect.height){
					Rectangle pre = S.top(); S.pop();
					int area = pre.height * (i - pre.pos);
					maxv= max(maxv, area);
					target = pre.pos;
				}
				rect.pos = target;
				S.push(rect);
			}
		}
	}
	return maxv;
}

int H, W;
int buffer[MAX][MAX];
int T[MAX][MAX];

int getLargestRectangle(){
	for(int j = 0; j < W; j++){
		for(int i = 0; i < H; i++){
			if(buffer[i][j]){
				T[i][j] = 0;
			}else{
				T[i][j] = (i > 0) ? T[i - 1][j] + 1 : 1;
			}
		}
	}

	int maxv = 0;
	for(int i = 0; i < H; i++){
		maxv = max(maxv, getLargestRectangle(W, T[i]));
	}

	return maxv;
}

int main(){
	scanf("%d %d", &H, &W);
	for(int i = 0; i < H; i++){
		for(int j = 0; j < W; j++){
			scanf("%d", &buffer[i][j]);
		}
	}
	cout << getLargestRectangle() << endl;

	return 0;
}