#include <fstream>
using namespace std;
ifstream fin ("bmatrix.in");
ofstream fout("bmatrix.out");
int n,m,q,p,x,i,j,SL[201][201],SC[201][201],a[201][201],maxim1,maxim2,sol,i1,j1,ac[201][201],sc[201][201],sl[201][201];
char s[211];
int main()
{
    fin>>n>>m;
    for(i=1;i<=n;i++)
    {
        fin>>s;
        for(j=1;j<=m;j++)
        {
            a[i][j]=s[j-1]-'0';
            ac[i][j]=a[i][j];
        }
    }
    for(i=1;i<=n;i++)
    {
        for(j=1;j<=m;j++)
        {
            if(!a[i][j])
            {
                SL[i][j]=SL[i][j-1]+1;
                SC[i][j]=SC[i-1][j]+1;
            }
        }
    }
    //dupa linie
    for(i=1;i<=n;i++)
    {
        for(j=1;j<=m;j++)
            if(SL[i][j]>=SC[i][j]&&SL[i][j]*SC[i][j]>maxim1)
            {
                maxim1=SL[i][j]*SC[i][j];
                i1=i;
                j1=j;
            }
    }
    for(i=i1;i>=i1-SC[i1][j1]+1;i--)
    {
        for(j=j1;j>=j1-SL[i1][j1]+1;j--)
            ac[i][j]=1;
    }
    for(i=1;i<=n;i++)
    {
        for(j=1;j<=m;j++)
        {
            if(!ac[i][j])
            {
                sl[i][j]=sl[i][j-1]+1;
                sc[i][j]=sc[i-1][j]+1;
            }
        }
    }
    for(i=1;i<=n;i++)
    {
        for(j=1;j<=m;j++)
            if(sl[i][j]>=sc[i][j]&&sl[i][j]*sc[i][j]>maxim2)
            {
                maxim2=sl[i][j]*sc[i][j];
                i1=i;
                j1=j;
            }

    }
    sol=max(sol,maxim1+maxim2);
    //fout<<sol<<"\n";
    maxim1=0;
    maxim2=0;
    for(i=1;i<=n;i++)
        for(j=1;j<=m;j++)
        {
            sl[i][j]=0;
            sc[i][j]=0;
            ac[i][j]=a[i][j];
        }
    //dupa coloana
    for(i=1;i<=n;i++)
    {
        for(j=1;j<=m;j++)
            if(SL[i][j]<=SC[i][j]&&SL[i][j]*SC[i][j]>maxim1)
            {
                maxim1=SL[i][j]*SC[i][j];
                i1=i;
                j1=j;
            }
    }
    for(i=i1;i>=i1-SC[i1][j1]+1;i--)
    {
        for(j=j1;j>=j1-SL[i1][j1]+1;j--)
            ac[i][j]=1;
    }
    /*for(i=1;i<=n;i++)
    {
        for(j=1;j<=m;j++)
            fout<<ac[i][j];
        fout<<"\n";
    }*/
    for(i=1;i<=n;i++)
    {
        for(j=1;j<=m;j++)
        {
            if(!ac[i][j])
            {
                sl[i][j]=sl[i][j-1]+1;
                sc[i][j]=sc[i-1][j]+1;
            }
        }
    }
    for(i=1;i<=n;i++)
    {
        for(j=1;j<=m;j++)
            if(sl[i][j]<=sc[i][j]&&sl[i][j]*sc[i][j]>maxim2)
            {
                maxim2=sl[i][j]*sc[i][j];
                i1=i;
                j1=j;
            }
    }
    sol=max(sol,maxim1+maxim2);

    fout<<sol;
    return 0;
}