#include<bits/stdc++.h>
#define maxn 1000
#define maxm 1000
using namespace std;

int M[maxn][maxm] ;

int main( )
  {
   // freopen("fin.txt","r",stdin);
  //  freopen("fout.txt","w",stdout);

      int n,m;
      int sol;
      char c;
      cin>> n >> m;

      for(int i = 0 ; i < n ; ++i ){
        for(int j = 0 ; j < m ; ++j ){
        cin>>c;
      if(c!='&'){
      if(i==0 && j==0){ M[i][j]=1;}
      else if(i==0){ M[i][j]=M[i][j-1]+1; }
      else if(j==0){M[i][j]=M[i-1][j]+1;}
      else M[i][j]=max(M[i][j-1],M[i-1][j])+1;

      }

      else M[i][j]=0;

      sol=max(M[i][j],sol);

}

}

       cout << sol;




      return 0;
  }