#include <algorithm>
#include <iostream>
#include <fstream>
#define pb push_back
#define mp make_pair
#define ld long double
#define ll long long
#define ull unsigned long long
using namespace std;
#define f cin
#define g cout
#define Block -1
//ifstream f("gigel.in");
//ofstream g("gigel.out");

int N,M,a[110][110],b[110][110],sol;


void Fill(int i,int j)
{
     a[i][j]=max(a[i][j],1);
     sol=max(sol,a[i][j]);
     if(j<N && (a[i][j+1]<a[i][j]+1 || !a[i][j+1]) && a[i][j+1]!=Block)
     {
          a[i][j+1]=a[i][j]+1;
          Fill(i,j+1);
     }
     if(i<M && (a[i+1][j]<a[i][j]+1 || !a[i+1][j]) && a[i+1][j]!=Block)
     {
          a[i+1][j]=a[i][j]+1;
          Fill(i+1,j);
     }
}
int main()
{
     f>>M>>N;
     for(int i=1;i<=M;++i)
          for(int j=1;j<=N;++j)
          {
               char c;
               f>>c;
               if(c=='&')a[i][j]=Block;
          }
     for(int i=1;i<=M;++i)
          for(int j=1;j<=N;++j)
          if(a[i][j]!=Block)
          {
               Fill(i,j);
          }
     //for(int i=1;i<=M;++i,g<<'\n')
          ///for(int j=1;j<=N;++j)g<<a[i][j]<<' ';
     g<<sol<<'\n';
     //f.close();g.close();
     return 0;
}