import java.awt.Point;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayDeque;
import java.util.Deque;
import java.util.NoSuchElementException;

public class Main {

	public static void main(String[] args) {

		FastScanner sc = new FastScanner();

		int h = sc.nextInt();
		int w = sc.nextInt();

		Point start = new Point(0, 0);
		Point goal = new Point(w - 1, h - 1);

		//定数D4
		Point[] D4 = { new Point(0, -1), new Point(1, 0), new Point(0, 1), new Point(-1, 0) };

		char[][] c = new char[h][w];

		for (int i = 0; i < h; i++) {
			String line = sc.next();
			for (int j = 0; j < w; j++) {
				c[i][j] = line.charAt(j);
			}
		}

		int count = 0;
		for (int i = 0; i < h; i++) {
			for (int j = 0; j < w; j++) {
				if (c[i][j] == '.')
					count++;
			}
		}

		//Queueを用意し、スタート地点を入れる
		Deque<Point> queue = new ArrayDeque<>();
		queue.add(start);

		//各地点のスタート地点からの距離を記録する二次元配列
		int[][] moves = new int[h][w];

		//スタート地点を"#"で埋めて、探索済みにする
		c[start.y][start.x] = '#';

		//幅優先探索
		while (queue.size() > 0) {

			//Queueの先頭の座標を取り出し＆削除して、その四方を探索する。
			Point p = queue.poll();

			for (int i = 0; i < 4; i++) {

				int x = p.x + D4[i].x;
				int y = p.y + D4[i].y;
				if ((x < 0 || y < 0) || (y >= h || x >= w))
					continue;
				if (c[y][x] == '.') {

					//"."であれば探索可能なので、Queueの末尾に追加する
					queue.add(new Point(x, y));

					//探索が終わった座標を"#"で埋めて、次回以降探索しないようにする
					c[y][x] = '#';

					//座標pからpの四方の座標への移動距離は、pまでの移動距離+1
					moves[y][x] = moves[p.y][p.x] + 1;

				}

			}

		}

		//ゴール地点に相当するmovesの値が答え
		if (moves[goal.y][goal.x] == 0)
			System.out.println(-1);
		else
			System.out.println(count - moves[goal.y][goal.x] - 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: 21972