#include <bits/stdc++.h>
using namespace std;
#define all(c) (c).begin(),(c).end()
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;i--)
#define REP(i,m,n) for(int i=(int)(m);i<(int)(n);i++)
#define rep(i,n) REP(i,0,n)
#define iter(c) __typeof((c).begin())
#define tr(it,c) for(iter(c) it=(c).begin();it!=(c).end();it++)
#define pb(a) push_back(a)
#define pr(a) cout<<(a)<<endl
#define PR(a,b) cout<<(a)<<" "<<(b)<<endl
#define R cin>>
#define F first
#define S second
#define ll long long
bool check(int n,int m,int x,int y){return (x<0||x>=n||y<0||y>=m)?false:true;}
const ll MAX=1000000007,MAXL=1LL<<60,dx[4]={-1,0,1,0},dy[4]={0,1,0,-1};
typedef pair<int,int> P;
typedef pair<P,int> P2;

int n,m,a[50][50];
string s[50];

void dfs(int x, int y, int k) {
  a[x][y]=k;
  rep(i,4) {
    int nx=x+dx[i],ny=y+dy[i];
    if(check(n,m,nx,ny) && s[nx][ny]=='.' && !a[nx][ny]) dfs(nx,ny,k);
  }
}

int main() {
  cin >> m >> n;
  rep(i,n) cin >> s[i];
  int k=1;
  rep(i,n) {
    rep(j,m) {
      if(s[i][j]!='#' && !a[i][j]) dfs(i,j,k++);
    }
  }
  k--;
  int d[n][m],dp[1<<k];
  fill(d[0],d[n],MAX);
  fill(dp,dp+(1<<k),MAX);
  dp[1]=0;
  queue<P2> que;
  rep(i,n) rep(j,m) if(a[i][j]==1) {
    que.push(P2(P(i,j),1));
    d[i][j]=0;
  }
  while(!que.empty()) {
    P2 p=que.front();que.pop();
    int nx=p.F.F,ny=p.F.S,t=p.S;
    rep(i,4) {
      int x=nx+dx[i],y=ny+dy[i];
      if(!check(n,m,x,y)) continue;
      if(a[x][y]>1) {
	if(d[x][y]>d[nx][ny]) {
	  d[x][y]=d[nx][ny];
	  que.push(P2(P(x,y),t|(1<<(a[x][y]-1))));
	}
	dp[t|(1<<(a[x][y]-1))]=min(dp[t|(1<<(a[x][y]-1))],dp[t]+d[nx][ny]);
      } else {
	if(d[x][y]>d[nx][ny]+1) {
	  d[x][y]=d[nx][ny]+1;
	  que.push(P2(P(x,y),t));
	}
      }
    }
  }
  cout << dp[(1<<k)-1] << endl;
  return 0;
}