#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