Problem:
Largest Rectangle

Given a matrix (H × W) which contains only 1 and 0, find the area of the largest rectangle which only contains 0s.

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.

Constraints

1 ≤ H, W ≤ 1,400

Sample Input

4 5
0 0 1 0 0
1 0 0 0 0
0 0 0 1 0
0 0 0 1 0

Sample Output

6

Solution in JavaScript (judge verdict: Time Limit Exceeded)

//usr/bin/env node --harmony $0 $@;exit
var main=function(){
	var arg=readline().split(' ').map(Number);
	var y=arg[0],x=arg[1];
	var m=Array(y);
	for(var j=0;j<y;j++){
		arg=readline().split(' ').map(Number);
		r=0;
		m[j]=Array(x);
		for(var i=0;i<x;m[j][i]=r,i++){
			r=arg[i]==0?r+1:0;
		}
	}
	var r=0;
	for(var i=0;i<x;i++)for(var j=0;j<y;j++)for(var M=x,k=j;k<y;k++){
		if(M>m[k][i])M=m[k][i];
		var z=k-j+1;
		if(r<M*z)r=M*z;
	}
	print(r);
}
// 制限時間厳しくないですか… //

/// IO ///
if(typeof process!=='undefined'){
	//node.js
	var print=function(x){
		console.log(x);
	}
	var readline=(function(){
		var T=[],cnt=0;
		var stdin = process.openStdin();
		stdin.setEncoding('utf8');

		var input_fragment="";
		stdin.on('data', function(input) {
			var ref=(input_fragment+input).split("\n");
			input_fragment=ref.pop();
			for(var i=0;i<ref.length;i++){
				if(ref[i]=='')continue;
				T.push(ref[i]);
			}
		});
		stdin.on('end', function(z) {
			if(input_fragment){
				var ref=(input_fragment+"\n").split("\n");
				input_fragment=ref.pop();
				for(var i=0;i<ref.length;i++){
					if(ref[i]=='')continue;
					T.push(ref[i]);
				}
			}
			main();
		});

		return function(){
			if(T.length<=cnt)return null;
			return T[cnt++];
		};
	})();
}else{
	//v8
	main();
}