#include<cstdio>

 #include<cstring>

 #include<cmath>

 #include<algorithm>

 #define CLR(a,b) memset((a),(b),sizeof((a)))

 using namespace std;

 const int N = ;

 const int inf = 0x3f3f3f3f;

 int n, m;

 int dp[N][N];

 int main(){

     int i, j, k, ans, x, h;

     scanf("%d%d", &m, &n);

     CLR(dp, );

     for(i = ; i <= n; ++i){

         for(j = ; j <= m; ++j){

             scanf("%d", &x);

             if(x) dp[i][j] = x + dp[i-][j];

         }

     }

     ans = ;

     for(i = ; i <= m; ++i){

         for(j =  ; j <= n; ++j){

             h = inf;

             for(k = i; k <= m; ++k){

                 h = min(h, dp[j][k]);

                 if(h == ) break;

                 ans = max(ans, (k-i+) * h);

             }

         }

     }

     printf("%d\n", ans);

     return ;

 }