#include<iostream>
using namespace std;
int i,j,n,m,a[105][104],sol;
char ch;

int main(void) {
    cin>>n>>m;
    for (i=1; i<=n; ++i)
     for (j=1; j<=m; ++j) {
           cin>>ch;
           if (ch=='.') a[i][j]=0;
            else a[i][j]=-1;
            }
            
   if (a[1][1]==-1) cout<<0;
    else {
         for (i=1; i<=n; ++i)
          for (j=1; j<=n; ++j)
           if (a[i][j]==0&&a[i-1][j]==-1&&a[i][j-1]==-1) a[i][j]=-1;
           else if (a[i][j]==0) {
                           a[i][j]=1+max(a[i-1][j],a[i][j-1]);
                           sol=max(sol,a[i][j]);
                           }
           }
    cout<<sol;
   return(0);
}