import java.io.IOException;
import java.io.InputStream;
import java.util.*;

class Pair {
    int id, prevColor;

    public Pair(int id, int prevColor) {
        this.id = id;
        this.prevColor = prevColor;
    }
}

public class Main {

    static void bfs() {
        visited = new boolean[H][W];
        visited[0][0] = true;
        dist[0][0] = 1;
        Deque<Integer> Y = new ArrayDeque<>();
        Deque<Integer> X = new ArrayDeque<>();
        Y.offer(0);
        X.offer(0);

        while (!Y.isEmpty()) {
            int h = Y.poll();
            int w = X.poll();

            for (int i = 0; i < 4; ++i) {
                int nh = h + dy[i];
                int nw = w + dx[i];

                if (nh < 0 || nh >= H || nw < 0 || nw >= W) continue;
                if (visited[nh][nw]) continue;
                if (grid[nh][nw] == '#') continue;

                visited[nh][nw] = true;
                dist[nh][nw] = dist[h][w] + 1;
                Y.offer(nh);
                X.offer(nw);
            }
        }
    }

    static int H, W, white;
    static char[][] grid;
    static boolean[][] visited;
    static int[][] dist;
    static int[] dy = {1, -1, 0, 0};
    static int[] dx = {0, 0, 1, -1};

    public static void main(String[] args) {
        FastScanner fs = new FastScanner();
        H = fs.nextInt();
        W = fs.nextInt();
        grid = new char[H][W];
        dist = new int[H][W];
        for (int i = 0; i < H; ++i) Arrays.fill(dist[i], 0);
        for (int i = 0; i < H; ++i) {
            grid[i] = fs.next().toCharArray();
            for (int j = 0; j < W; ++j) {
                if (grid[i][j] == '.') ++white;
            }
        }

        bfs();

        if (visited[H-1][W-1])
            System.out.println(white - dist[H-1][W-1]);
        else
            System.out.println(-1);

    }
}

class FastScanner {
    private final InputStream in = System.in;
    private final byte[] buffer = new byte[1024];
    private int ptr = 0;
    private int buflen = 0;

    private boolean hasNextByte() {
        if (ptr < buflen) {
            return true;
        }else{
            ptr = 0;
            try {
                buflen = in.read(buffer);
            } catch (IOException e) {
                e.printStackTrace();
            }
            if (buflen <= 0) {
                return false;
            }
        }
        return true;
    }

    private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
    private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
    public boolean hasNext() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++; return hasNextByte();}

    public String next() {
        if (!hasNext()) throw new NoSuchElementException();
        StringBuilder sb = new StringBuilder();
        int b = readByte();
        while(isPrintableChar(b)) {
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }

    public long nextLong() {
        if (!hasNext()) throw new NoSuchElementException();
        long n = 0;
        boolean minus = false;
        int b = readByte();
        if (b == '-') {
            minus = true;
            b = readByte();
        }
        if (b < '0' || '9' < b) {
            throw new NumberFormatException();
        }
        while(true){
            if ('0' <= b && b <= '9') {
                n *= 10;
                n += b - '0';
            }else if(b == -1 || !isPrintableChar(b)){
                return minus ? -n : n;
            }else{
                throw new NumberFormatException();
            }
            b = readByte();
        }
    }

    public int nextInt() {
        long nl = nextLong();
        if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) throw new NumberFormatException();
        return (int) nl;
    }

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





























Measured memory_bytes: 22100