#include<cstdio>

#include<cstring>

#include<cmath>

#include<algorithm>

using namespace std;

const int maxn=+;

int a[maxn];

int L[maxn],R[maxn];

int m,n;

int tmp[maxn][maxn],b[maxn][maxn];

void f()

{

    for(int i=; i<=n; i++) L[i]=i;

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

    {

        if(a[i]>a[i-]) continue;

        int pre=L[i-];

        while()

        {

            L[i]=pre;

            if(pre==||a[pre-]<a[i]) break;

            pre=L[pre-];

        }

    }

    for(int i=n; i>=; i--) R[i]=i;

    for(int i=n-; i>=; i--)

    {

        if(a[i]>a[i+]) continue;

        int pre=R[i+];

        while()

        {

            R[i]=pre;

            if(pre==n||a[pre+]<a[i]) break;

            pre=R[pre+];

        }

    }

}

int main()

{

    while(~scanf("%d%d",&n,&m))

    {

        memset(b,,sizeof b);

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

            for(int j=; j<=m; j++) scanf("%d",&tmp[i][j]);

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

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

            {

                if(tmp[i][j]==) continue;

                b[i][j]=b[i][j-]+tmp[i][j];

            }

        int ans=;

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

        {

            for(int i=;i<=n;i++) a[i]=b[i][j];

            f();

            for(int i=;i<=n;i++) ans=max(ans,a[i]*(R[i]-L[i]+));

        }

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

    }

    return ;

}