#include<cstdio>
#include<algorithm>
#include<cstring>
#define Nmax 205
using namespace std;
int n,m,i,j,p,sol,nr,a[Nmax][Nmax],s[Nmax][Nmax];
int u[Nmax],d[Nmax];
char b[Nmax][Nmax];
using namespace std;
struct nod1
{
    int h;
    int poz;
}st[Nmax];
struct nod2
{
    int x;
    int y;
    int z;
}U[Nmax];
void citire()
{
    scanf("%d %d\n",&n,&m);
    for (i=1;i<=n;i++)
    gets(b[i]+1);
}
void lmax0()
{
    int i,j,k,nr,A,l=0;
    for (i=1;i<=n;i++)
    {
        for (j=1;j<=m;j++)
        if (b[i][j]=='0')
        a[i][j]=a[i-1][j]+1;
        else a[i][j]=0;
    }
    for (i=1;i<=n;l=0,i++)
    for (j=1;j<=m+1;j++)
    {
        if (j==1) l=0;
        if (a[i][j]>st[l].h)
        {
            st[++l].h=a[i][j];
            st[l].poz=j;
            continue;
        }
        while (l>0 && a[i][j]<=st[l].h)
        {
            A=(j-st[l].poz)*st[l].h;
            if (A>u[i])
            {u[i]=A; U[i].x=st[l].poz; U[i].y=j-1; U[i].z=st[l].h;}
            l--;
        }
        if (a[i][j]>0)
        st[++l].h=a[i][j];
    }
    for (i=2;i<=n;i++)
    if(u[i]>u[i-1])
    p=i;
    else u[i]=u[i-1];
}
int main()
{
    freopen("bmatrix.in","r",stdin);
    freopen("bmatrix.out","w",stdout);
    citire();
    lmax0();
    sol=u[n];
    for (i=U[p].x;i<=U[p].y;i++)
    for (j=p;j>=p-U[p].z+1;j--)
    b[j][i]='1';
    memset(u,0,sizeof(u));
    memset(a,0,sizeof(a));
    lmax0();
    sol+=u[n];
    printf("%d",sol);
    return 0;
}