using System;
using System.Text;
using System.Collections.Generic;
using System.Linq;
class Solve{
    public Solve(){}
    StringBuilder sb;
    ReadData re;
    public static int Main(){
        new Solve().Run();
        return 0;
    }
    void Run(){
        sb = new StringBuilder();
        re = new ReadData();
        Calc();
        Console.Write(sb.ToString());
    }
    void Calc(){
        int H = re.i();
        int W = re.i();
        int[,] Map = new int[H,W];
        int count = 0;
        for(int i=0;i<H;i++){
            string s = re.s();
            for(int j=0;j<W;j++){
                if(s[j] == '.'){
                    Map[i,j] = count;
                    count++;
                }
                else{
                    Map[i,j] = -1;
                }
            }
        }
        List<int> f = new List<int>();
        List<int> t = new List<int>();
        List<long> cost = new List<long>();
        for(int i=0;i<H-1;i++){
            for(int j=0;j<W;j++){
                if(Map[i,j] != -1 && Map[i+1,j] != -1){
                    f.Add(Map[i,j]);
                    t.Add(Map[i+1,j]);
                    cost.Add(1);
                    t.Add(Map[i,j]);
                    f.Add(Map[i+1,j]);
                    cost.Add(1);
                }
            }
        }
        for(int i=0;i<H;i++){
            for(int j=0;j<W-1;j++){
                if(Map[i,j] != -1 && Map[i,j+1] != -1){
                    f.Add(Map[i,j]);
                    t.Add(Map[i,j+1]);
                    cost.Add(1);
                    t.Add(Map[i,j]);
                    f.Add(Map[i,j+1]);
                    cost.Add(1);
                }
            }
        }
        Dijkstra D = new Dijkstra(f.ToArray(),t.ToArray(),cost.ToArray(),count,0);
        long ans = count - D.GetCost(count-1);
        if(D.GetCost(count-1) == -1){
            sb.Append("-1\n");
            return;
        }
        sb.Append(ans-1+"\n");
    }
}
struct Edge{
    public Vertex v;
    public long cost;
    public Edge(Vertex v0,long c){
        v = v0;
        cost = c;
    }
}
class Vertex{
    public bool finished;
    public List<Vertex> edges;
    public List<long> costs;
    public long cost;
    public void AddEdge(Vertex v,long c){
        edges.Add(v);
        costs.Add(c);
    }
    public Vertex(){
        edges = new List<Vertex>();
        costs = new List<long>();
        cost = -1;
        finished = false;
    }
}
class Dijkstra{
	int E;
	Vertex[] point;
    Vertex S;
    public long GetCost(int i){
        return point[i].cost;
    }
    public Dijkstra(int[] f,int[] t,long[] cost,int n,int s){
        point = new Vertex[n];
        for(int i=0;i<n;i++){
            point[i] = new Vertex();
        }
        E = f.Length;
        for(int i=0;i<E;i++){
            point[f[i]].AddEdge(point[t[i]],cost[i]);
        }
        S = point[s];
        calc();
    }
    void calc(){
        Heap H = new Heap(2*E+1);
        S.cost = 0;
        H.push(new Edge(S,0));
        while(!H.Empty()){
            Vertex v = H.pop().v;
            if(v.finished){
                continue;
            }
            v.finished = true;
            for(int i=0;i<v.edges.Count;i++){
                Vertex vi = v.edges[i];
                if(vi.cost == -1 || vi.cost > v.costs[i]+v.cost){
                    vi.cost = v.costs[i]+v.cost;
                    H.push(new Edge(vi,vi.cost));
                }
            }
        }
    }
}
class Heap{
    public int size;
    Edge[] obj;
    public Heap(int maxsize){
        size = 0;
        obj = new Edge[maxsize];
    }
    public void push(Edge a){
        int i = size;
        size++;
        while(i > 0){
            int p = (i - 1)/2;
            if(obj[p].cost <= a.cost){
                obj[i] = a;
                break;
            }
            obj[i] = obj[p];
            i = p;
        }
        if(i == 0){
            obj[0] = a;
        }
    }
    public bool Empty(){
        return size == 0;
    }
    public Edge pop(){
        Edge t = obj[0];
        int i = 0;
        size--;
        while(2*i+1 < size){
            int p = 2*i+1;
            if(p+1 < size && obj[p+1].cost < obj[p].cost){
                p++;
            }
            if(obj[p].cost < obj[size].cost){
                obj[i] = obj[p];
                i = p;
            }
            else{
                obj[i] = obj[size];
                break;
            }
        }
        if(2*i+1 >= size){
            obj[i] = obj[size];
        }
        return t;
    }
}
class ReadData{
    string[] str;
    int counter;
    public ReadData(){
        counter = 0;
    }
    public string s(){
        if(counter == 0){
            str = Console.ReadLine().Split(' ');
            counter = str.Length;
        }
        counter--;
        return str[str.Length-counter-1];
    }
    public int i(){
        return int.Parse(s());
    }
    public long l(){
        return long.Parse(s());
    }
    public double d(){
        return double.Parse(s());
    }
    public int[] ia(int N){
        int[] ans = new int[N];
        for(int j=0;j<N;j++){
            ans[j] = i();
        }
        return ans;
    }
    public int[] ia(){
        str = Console.ReadLine().Split(' ');
        counter = 0;
        int[] ans = new int[str.Length];
        for(int j=0;j<str.Length;j++){
            ans[j] = int.Parse(str[j]);
        }
        return ans;
    }
    public long[] la(int N){
        long[] ans = new long[N];
        for(int j=0;j<N;j++){
            ans[j] = l();
        }
        return ans;
    }
    public long[] la(){
        str = Console.ReadLine().Split(' ');
        counter = 0;
        long[] ans = new long[str.Length];
        for(int j=0;j<str.Length;j++){
            ans[j] = long.Parse(str[j]);
        }
        return ans;
    }
    public double[] da(int N){
        double[] ans = new double[N];
        for(int j=0;j<N;j++){
            ans[j] = d();
        }
        return ans;
    }
    public double[] da(){
        str = Console.ReadLine().Split(' ');
        counter = 0;
        double[] ans = new double[str.Length];
        for(int j=0;j<str.Length;j++){
            ans[j] = double.Parse(str[j]);
        }
        return ans;
    }
    public List<int>[] g(int N,int[] f,int[] t){
        List<int>[] ans = new List<int>[N];
        for(int j=0;j<N;j++){
            ans[j] = new List<int>();
        }
        for(int j=0;j<f.Length;j++){
            ans[f[j]].Add(t[j]);
            ans[t[j]].Add(f[j]);
        }
        return ans;
    }
    public List<int>[] g(int N,int M){
        List<int>[] ans = new List<int>[N];
        for(int j=0;j<N;j++){
            ans[j] = new List<int>();
        }
        for(int j=0;j<M;j++){
            int f = i()-1;
            int t = i()-1;
            ans[f].Add(t);
            ans[t].Add(f);
        }
        return ans;
    }
    public List<int>[] g(){
        int N = i();
        int M = i();
        List<int>[] ans = new List<int>[N];
        for(int j=0;j<N;j++){
            ans[j] = new List<int>();
        }
        for(int j=0;j<M;j++){
            int f = i()-1;
            int t = i()-1;
            ans[f].Add(t);
            ans[t].Add(f);
        }
        return ans;
    }
}
public static class Define{
    public const long mod = 1000000007;
}
public static class Debug{
    public static void Print(double[,,] k){
        for(int i=0;i<k.GetLength(0);i++){
            for(int j=0;j<k.GetLength(1);j++){
                for(int l=0;l<k.GetLength(2);l++){
                    Console.Write(k[i,j,l]+" ");
                }
                Console.WriteLine();
            }
            Console.WriteLine();
        }
    }
    public static void Print(double[,] k){
        for(int i=0;i<k.GetLength(0);i++){
            for(int j=0;j<k.GetLength(1);j++){
                Console.Write(k[i,j]+" ");
            }
            Console.WriteLine();
        }
    }
    public static void Print(double[] k){
        for(int i=0;i<k.Length;i++){
            Console.WriteLine(k[i]);
        }
    }
    public static void Print(long[,,] k){
        for(int i=0;i<k.GetLength(0);i++){
            for(int j=0;j<k.GetLength(1);j++){
                for(int l=0;l<k.GetLength(2);l++){
                    Console.Write(k[i,j,l]+" ");
                }
                Console.WriteLine();
            }
            Console.WriteLine();
        }
    }
    public static void Print(long[,] k){
        for(int i=0;i<k.GetLength(0);i++){
            for(int j=0;j<k.GetLength(1);j++){
                Console.Write(k[i,j]+" ");
            }
            Console.WriteLine();
        }
    }
    public static void Print(long[] k){
        for(int i=0;i<k.Length;i++){
            Console.WriteLine(k[i]);
        }
    }
    public static void Print(int[,,] k){
        for(int i=0;i<k.GetLength(0);i++){
            for(int j=0;j<k.GetLength(1);j++){
                for(int l=0;l<k.GetLength(2);l++){
                    Console.Write(k[i,j,l]+" ");
                }
                Console.WriteLine();
            }
            Console.WriteLine();
        }
    }
    public static void Print(int[,] k){
        for(int i=0;i<k.GetLength(0);i++){
            for(int j=0;j<k.GetLength(1);j++){
                Console.Write(k[i,j]+" ");
            }
            Console.WriteLine();
        }
    }
    public static void Print(int[] k){
        for(int i=0;i<k.Length;i++){
            Console.WriteLine(k[i]);
        }
    }
}


Measured memory_bytes: 14176