import java.io.*;
import java.util.*;

/**
 *
 * @author baito
 */
public class Main
{
    static StringBuilder sb = new StringBuilder();
    static FastScanner sc = new FastScanner(System.in);
    static int H,W;
    static char[][] A;
    static int[][] d;
    static int INF = 100;
    public static void main(String[] args)
    {

        H = sc.nextInt();
        W = sc.nextInt();
        A = sc.nextWrapCharArray2(H,W,'*');
        d = new int[H + 2][W +2];
        fill(d,INF);
        //longを忘れるなオーバーフローするぞ
        int wall = countC2(A,'#');

        LinkedList<Integer> q = new LinkedList<>();
        q.add(1);
        q.add(1);
        d[1][1] = 1;
        //y,x
        int ans,manpokei ;
        while (q.size() != 0)
        {
            int y = q.poll();
            int x = q.poll();
            int[] w = {1,0,-1,0,1};
            for (int i = 0; i < 4; i++)
            {
                int ny = y + w[i];
                int nx = x + w[i+1];
                if(A[ny][nx] == '*' || A[ny][nx] == '#' || d[ny][nx] != INF)
                    continue;
                q.add(ny);
                q.add(nx);
                d[ny][nx] = d[y][x] + 1;

                if((ny == H) && (nx == W)){
                    manpokei = d[H][W];
                    ans = H * W - manpokei - wall;
                    System.out.println(ans);
                    return ;
                }
            }
        }
        System.out.println("-1");



    }


    static int gcd(int n, int r) { return r == 0 ? n : gcd(r, n%r); }
    static long gcd(long n, long r) { return r == 0 ? n : gcd(r, n%r); }

    static <T> void swap(T[] x, int i, int j) { T t = x[i]; x[i] = x[j]; x[j] = t; }
    static void swap(int[] x, int i, int j) { int t = x[i]; x[i] = x[j]; x[j] = t; }
    public static void reverse(int[] x)
    {
        int l = 0;
        int r = x.length - 1;
        while (l < r)
        {
            int temp = x[l];
            x[l] = x[r];
            x[r] = temp;
            l++;
            r--;
        }
    }
    static int length(int a) {int cou = 0; while(a != 0){ a /= 10; cou++; } return cou;}
    static int length(long a) {int cou = 0; while(a != 0){ a /= 10; cou++; } return cou;}
    static int countC2(char[][] a, char c){
        int co = 0;
        for (int i = 0; i < a.length; i++)
            for (int j = 0; j < a[0].length; j++)
                if(a[i][j] == c)
                    co++;
        return co;
    }
    static void fill(int[][] a, int v){
        for (int i = 0; i < a.length; i++)
            for (int j = 0; j < a[0].length; j++)
                a[i][j] = v;
    }
    static class FastScanner {

        private BufferedReader reader = null;
        private StringTokenizer tokenizer = null;

        public FastScanner(InputStream in) {
            reader = new BufferedReader(new InputStreamReader(in));
            tokenizer = null;
        }

        public String next() {
            if (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }
        /*public String nextChar(){
            return (char)next()[0];
        }*/
        public String nextLine() {
            if (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    return reader.readLine();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }

            return tokenizer.nextToken("\n");
        }

        public long nextLong() {
            return Long.parseLong(next());
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

        public double nextDouble() {
            return Double.parseDouble(next());
        }

        public int[] nextIntArray(int n) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++) {
                a[i] = nextInt();
            }
            return a;
        }
        public int [][] nextIntArray2(int h, int w){
            int[][] a = new int[h][w];
            for(int hi = 0 ; hi < h ; hi++){
                for(int wi = 0 ; wi < w ; wi++){
                    a[hi][wi] = nextInt();
                }
            }
            return a;
        }
        public Integer[] nextIntegerArray(int n) {
            Integer[] a = new Integer[n];
            for (int i = 0; i < n; i++) {
                a[i] = nextInt();
            }
            return a;
        }
        public char[] nextCharArray(int n){
            char[] a = next().toCharArray();

            return a;
        }
        public char[][] nextCharArray2(int h , int w){
            char[][] a = new char[h][w];
            for (int i = 0; i < h; i++) {
                a[i] = next().toCharArray();
            }
            return a;
        }
        //スペースが入っている場合
        public char[][] nextCharArray2s(int h , int w){
            char[][] a = new char[h][w];
            for (int i = 0; i < h; i++) {
                a[i] = nextLine().replace(" ","").toCharArray();
            }
            return a;
        }
        public char[][] nextWrapCharArray2(int h , int w, char c){
            char[][] a = new char[h + 2][w + 2];
            //char c = '*';
            int i;
            for (i = 0; i < w + 2; i++)
                a[0][i] = c;
            for (i = 1; i < h + 1; i++) {
                a[i] = (c + next() + c).toCharArray();
            }
            for (i = 0; i < w + 2; i++)
                a[h + 1][i] = c;
            return a;
        }
        //スペースが入ってる時用
        public char[][] nextWrapCharArray2s(int h , int w ,char c){
            char[][] a = new char[h + 2][w + 2];
            //char c = '*';
            int i;
            for (i = 0; i < w + 2; i++)
                a[0][i] = c;
            for (i = 1; i < h + 1; i++) {
                a[i] = (c + nextLine().replace(" ","") + c).toCharArray();
            }
            for (i = 0; i < w + 2; i++)
                a[h + 1][i] = c;
            return a;
        }





        public long[] nextLongArray(int n) {
            long[] a = new long[n];
            for (int i = 0; i < n; i++) {
                a[i] = nextLong();
            }
            return a;
        }
        public long [][] nextLongArray2(int h, int w){
            long[][] a = new long[h][w];
            for(int hi = 0 ; hi < h ; hi++){
                for(int wi = 0 ; wi < h ; wi++){
                    a[h][w] = nextLong();
                }
            }
            return a;
        }
    }
}


Measured memory_bytes: 23252