#include<algorithm>
#include<iostream>
#include<vector>
#include<queue>
using namespace std;
typedef long long lint;
typedef vector<int>vi;
typedef pair<int,int>pii;
#define rep(i,n)for(int i=0;i<(int)(n);++i)

string s[50];
int d[50][50];

int main(){
  int h,w;
  cin>>h>>w;
  rep(i,h)
    cin>>s[i];
  rep(i,h)rep(j,w)d[i][j]=-1;
  queue<pii>q;
  q.push(pii(0,0));
  d[0][0]=0;
  int dx[4]={1,0,-1,0},dy[4]={0,1,0,-1};
  while(!q.empty()){
    pii t=q.front();q.pop();
    int x=t.first,y=t.second;
    if(s[x][y]=='#')continue;
    rep(dir,4){
      int nx=x+dx[dir],ny=y+dy[dir];
      if(nx<0||nx>=h||ny<0||ny>=w)continue;
      if(d[nx][ny]>=0)continue;
      d[nx][ny]=d[x][y]+1;
      q.push(pii(nx,ny));
    }
  }
  int black=0;
  rep(i,h)rep(j,w)if(s[i][j]=='#')black++;
  if(d[h-1][w-1]==-1)cout<<-1<<endl;
  else cout<<h*w-d[h-1][w-1]-1-black<<endl;
}
