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 <cstdio>
#include <stack>
#include <algorithm>
using namespace std;
static const int MAX = 1400;
struct Rectangle { int height, pos; };
int H, W;
int buffer[MAX][MAX];
int T[MAX][MAX];

int getLargestRectangleR(int idx, int size) {
    stack<Rectangle> S;
    int maxv = 0;
    T[idx][size] = 0;

    Rectangle rect, pre;
    for (int i = 0; i <= size; i++) {
        rect.height = T[idx][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) {
                    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 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, getLargestRectangleR(i, W));
    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]);
    }
    printf("%d\n", getLargestRectangle());
    return 0;
}

