#include <stdio.h>
#define maxl 210

int i,j,k,n,m,min,op,max,x;
bool a[maxl][maxl],b[maxl][maxl];
short int d[maxl][maxl];
short int c[maxl][maxl][maxl];
int l[maxl],r[maxl],up[maxl],down[maxl];
char s[maxl];

void bmatrix()
{
     for (i=1; i<=n; i++)
         for (j=1; j<=m; j++)
         {
            d[i][j]=0;
            if (a[i][j]==0)
            {
                if (d[i][j-1]!=0) d[i][j]=d[i][j-1]+1;
                else d[i][j]=1;
            }
            c[i][j][1]=d[i][j];
            if (!op)
            {
                if (c[i][j][1]>l[j]) l[j]=c[i][j][1];
                if (c[i][j][1]>up[i]) up[i]=c[i][j][1];
            }
            else
            {
                if (c[i][j][1]>r[j]) r[j]=c[i][j][1];
                if (c[i][j][1]>down[i]) down[i]=c[i][j][1];
            }
         }
         for (i=1; i<=n; i++)
             for (j=1; j<=m; j++)
                for (k=2; k<=n; k++)
                if (a[i-k+1][j]==0 && i-k+1>0)
                {
                    min=c[i][j][k-1];
                    if (d[i-k+1][j]<min) min=d[i-k+1][j];
                    c[i][j][k]=min;

                    x=c[i][j][k]*k;

                    if (!op)
                    {
                        if (x>l[j]) l[j]=x;
                        if (x>up[i]) up[i]=x;
                    }
                    else
                    {
                        if (x>r[j]) r[j]=x;
                        if (x>down[i]) down[i]=x;
                    }
                }
                else break;

     op=1-op;
}

int main()
{
    freopen("bmatrix.in","r",stdin);
    freopen("bmatrix.out","w",stdout);

    scanf("%d %d",&n,&m);
    for (i=1; i<=n; i++)
    {
        scanf("%s",s+1);
        for (j=1; j<=m; j++)
        {
            a[i][j]=s[j]-48;
            b[i][j]=a[i][j];
        }
    }

    bmatrix();

    for (i=1; i<=n; i++)
        for (j=1; j<=m; j++)
            a[i][j]=b[n-i+1][m-j+1];

    bmatrix();

    for (i=1; i<=n; i++)
    {
        if (up[i-1]>up[i]) up[i]=up[i-1];
        if (down[i-1]>down[i]) down[i]=down[i-1];
    }

    for (j=1; j<=m; j++)
    {
        if (l[j-1]>l[j]) l[j]=l[j-1];
        if (r[j-1]>r[j]) r[j]=r[j-1];
    }

    max=0;
    for (i=0; i<=m; i++)
        if (l[i]+r[m-i]>max) max=l[i]+r[m-i];

    for (i=0; i<=n; i++)
        if (up[i]+down[n-i]>max) max=up[i]+down[n-i];

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

    return 0;
}