#include <cstdio>#include <cstring>#include <string>#include <iostream>#include <map>#include <vector>#include <cmath>#include <stack>#include <queue>#include <cstdlib>#include <algorithm>using namespace std;typedef __int64 int64;typedef long long ll;#define M 50005#define N 1000005#define max_inf 0x7f7f7f7f#define min_inf 0x80808080#define mod 1000000007int m , n , top;int q[2005] , lef[2005] , rig[2005];int main(){int h[2005];int ans;while (~scanf("%d%d",&m,&n)){int i , j;ans = 0;memset(h , 0 , sizeof h);for (i = 0 ; i < m ; i++){top = 0;for (j = 0 ; j < n ; j++){int x;scanf("%d",&x);h[j]++;h[j] = x ? h[j] : 0;while (top > 0 && h[q[top-1]] > h[j]){rig[q[top-1]] = j-1;top--;}if (top <= 0)lef[j] = 0;else lef[j] = q[top-1]+1;q[top++] = j;}while (top)rig[q[top-1]] = n-1,top--;for (j = 0 ; j < n ; j++){int temp = (rig[j]-lef[j]+1)*h[j];ans = max(ans,temp);}}printf("%dn",ans);}return 0;}
