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 <stack>
using namespace std;

int main(){
	int h, w;
	cin >> h >> w;
	int64_t ans = 0, dp[2][w + 1]{};
	for(int i = 0; i < h; i++){
		for(int j = 0; j < w; j++){
			cin >> dp[i & 1][j];
			dp[i & 1][j] = !dp[i & 1][j];
			if(dp[i & 1][j] == 0) continue;
			dp[i & 1][j] += dp[!(i & 1)][j];
		}
		dp[i & 1][w] = 0;
		stack<int64_t> st;
		for(int j = 0; j < w; j++){
			if(st.empty()){
				st.emplace(dp[i & 1][j]);
				continue;
			}
			for(int64_t x = 1; !st.empty() && dp[i & 1][j] < st.top(); x++){
				st.pop();
				ans = max(ans, x * dp[i & 1][j]);
			}
		}
	}
	cout << ans << endl;
}