#include <cstdio>

 #include <cstring>

 #include <iostream>

 #include <vector>

 using namespace std;

 char str[][];

 int r[][];

 int c[][];

 int judge(int rx,int ry,int lx,int ly)

 {

     int i,j;

     for(i = lx;i <= rx;i ++)

     {

         for(j = ly;j <= ry;j ++)

         {

             if(str[i-][j-] == '')

             return ;

         }

     }

     return ;

 }

 int main()

 {

     int n,m,i,j,k,u,ans;

     scanf("%d%d",&n,&m);

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

     scanf("%s",str[i]);

     ans = ;

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

     {

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

         {

            if(str[i-][j-] == '')

            {

                r[i][j] = r[i-][j] + ;

                c[i][j] = c[i][j-] + ;

            }

            else

            {

                r[i][j] = ;

                c[i][j] = ;

            }

         }

     }

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

     {

         for(j = m;j >= ;j --)

         {

             for(k = ;k <= r[i][j];k ++)

             {

                 for(u = ;u <= c[i][j];u ++)

                 {

                     if(ans >= (k+u)*) continue;

                     if(judge(i,j,i-k+,j-u+))

                     {

                         ans = max(ans,(k+u)*);

                     }

                 }

             }

         }

     }

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

     return ;

 }