#include <iostream>
using namespace std;
int n,m,g[15][15],ans;
int main() {
    cin >> n >> m;
    for (int i=0;i<n; i++) for (int j=0;j<m;j++)
        cin >> g[i][j];
    for (int i=0;i<n;i++) for (int j=0;j<m;j++)
        for (int k=i,s;k<n;k++) {
            s=0;
            for (int l=j;l<m;l++) {
                bool ok=1;
                for (int r=i;r<=k;r++) if (!g[r][l]) {
                    ok=0;   break;
                }
                if (!ok) break;
                s++;
            }
            ans=max(ans,(k-i+1)*s);
        }
    cout << ans;
    return 0;
}

#define LL long long
using namespace std;
const int N = 15;
int n,m;
int a[N][N];
int h[N][N];
int ans;
int main(){
    cin>>n>>m;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            cin>>a[i][j];
            if(a[i][j]==1) h[i][j] = h[i-1][j] + 1;
            else h[i][j] = 0;
        }
    }
    for(int i=1;i<=n;i++){
        for(int l=1;l<=m;l++){
            int minh = 1e9;
            for(int r=l;r<=m;r++){
                minh = min(minh, h[i][r]);
                if(minh == 0) break;
                ans = max(ans, minh*(r-l+1));
            }
        }
    }
    cout<<ans<<endl;
    return 0;
}
//:)
//114514