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


public class Main {

	private static Scanner sc;
	private static Printer pr;

	private static void solve() {
		final int INF = Integer.MAX_VALUE;
		int[] dx = {1, -1, 0, 0};
		int[] dy = {0, 0, 1, -1};

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

		char[][] s = new char[h][];
		int black = 0;
		for (int i = 0; i < h; i++) {
			s[i] = sc.next().toCharArray();
			for (int j = 0; j < w; j++) {
				if (s[i][j] == '#') {
					black++;
				}
			}
		}

		int[][] cnt = new int[h][w];
		for (int i = 0; i < h; i++) {
			Arrays.fill(cnt[i], INF);
		}
		cnt[0][0] = 0;
		Queue<Pair> q = new ArrayDeque<>();
		q.add(new Pair(0, 0));
		while (!q.isEmpty()) {
			Pair e = q.remove();

			for (int i = 0; i < 4; i++) {
				int nx = e.a + dx[i];
				int ny = e.b + dy[i];

				if (nx < 0 || nx >= w || ny < 0 || ny >= h) {
					continue;
				}

				if (s[ny][nx] == '#' || cnt[ny][nx] != INF) {
					continue;
				}

				cnt[ny][nx] = cnt[e.b][e.a] + 1;
				q.add(new Pair(nx, ny));
			}
		}

		if (s[h - 1][w - 1] == '#' || s[0][0] == '#' || cnt[h - 1][w - 1] == INF) {
			pr.println(-1);
		} else {
//			pr.println(cnt[h - 1][w - 1]);
			pr.println(h * w - cnt[h - 1][w - 1] - 1 - black);
		}
	}

	private static class Pair implements Comparable<Pair> {
		int a;
		int b;

		Pair(int a, int b) {
			this.a = a;
			this.b = b;
		}

		@Override
		public int compareTo(Pair o) {
			if (a == o.a) {
				return Integer.compare(b, o.b);
			}

			return Integer.compare(a, o.a);
		}

		@Override
		public int hashCode() {
			return Integer.hashCode(a);
		}

		@Override
		public String toString() {
			// [xxx, xxxx]
			StringBuilder stmp = new StringBuilder(32);
			stmp.append('[');
			stmp.append(a);
			stmp.append(',');
			stmp.append(' ');
			stmp.append(b);
			stmp.append(']');

			return stmp.toString();
		}
	}

	// ---------------------------------------------------
	public static void main(String[] args) {
		sc = new Scanner(System.in);
		pr = new Printer(System.out);

		solve();

		pr.close();
		sc.close();
	}

	@SuppressWarnings("unused")
	private static class Scanner {
		BufferedReader br;

		Scanner (InputStream in) {
			br = new BufferedReader(new InputStreamReader(in));
		}

		private boolean isPrintable(int ch) {
			return ch >= '!' && ch <= '~';
		}

		private boolean isCRLF(int ch) {
			return ch == '\n' || ch == '\r' || ch == -1;
		}

		private int nextPrintable() {
			try {
				int ch;
				while (!isPrintable(ch = br.read())) {
					if (ch == -1) {
						throw new NoSuchElementException();
					}
				}

				return ch;
			} catch (IOException e) {
				throw new NoSuchElementException();
			}
		}

		String next() {
			try {
				int ch = nextPrintable();
				StringBuilder sb = new StringBuilder();
				do {
					sb.appendCodePoint(ch);
				} while (isPrintable(ch = br.read()));

				return sb.toString();
			} catch (IOException e) {
				throw new NoSuchElementException();
			}
		}

		int nextInt() {
			try {
				// parseInt from Integer.parseInt()
				boolean negative = false;
				int res = 0;
				int limit = -Integer.MAX_VALUE;
				int radix = 10;

				int fc = nextPrintable();
				if (fc < '0') {
					if (fc == '-') {
						negative = true;
						limit = Integer.MIN_VALUE;
					} else if (fc != '+') {
						throw new NumberFormatException();
					}
					fc = br.read();
				}
				int multmin = limit / radix;

				int ch = fc;
				do {
					int digit = ch - '0';
					if (digit < 0 || digit >= radix) {
						throw new NumberFormatException();
					}
					if (res < multmin) {
						throw new NumberFormatException();
					}
					res *= radix;
					if (res < limit + digit) {
						throw new NumberFormatException();
					}
					res -= digit;

				} while (isPrintable(ch = br.read()));

				return negative ? res : -res;
			} catch (IOException e) {
				throw new NoSuchElementException();
			}
		}

		long nextLong() {
			try {
				// parseLong from Long.parseLong()
				boolean negative = false;
				long res = 0;
				long limit = -Long.MAX_VALUE;
				int radix = 10;

				int fc = nextPrintable();
				if (fc < '0') {
					if (fc == '-') {
						negative = true;
						limit = Long.MIN_VALUE;
					} else if (fc != '+') {
						throw new NumberFormatException();
					}
					fc = br.read();
				}
				long multmin = limit / radix;

				int ch = fc;
				do {
					int digit = ch - '0';
					if (digit < 0 || digit >= radix) {
						throw new NumberFormatException();
					}
					if (res < multmin) {
						throw new NumberFormatException();
					}
					res *= radix;
					if (res < limit + digit) {
						throw new NumberFormatException();
					}
					res -= digit;

				} while (isPrintable(ch = br.read()));

				return negative ? res : -res;
			} catch (IOException e) {
				throw new NoSuchElementException();
			}
		}

		float nextFloat() {
			return Float.parseFloat(next());
		}

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

		String nextLine() {
			try {
				int ch;
				while (isCRLF(ch = br.read())) {
					if (ch == -1) {
						throw new NoSuchElementException();
					}
				}
				StringBuilder sb = new StringBuilder();
				do {
					sb.appendCodePoint(ch);
				} while (!isCRLF(ch = br.read()));

				return sb.toString();
			} catch (IOException e) {
				throw new NoSuchElementException();
			}
		}

		void close() {
			try {
				br.close();
			} catch (IOException e) {
//				throw new NoSuchElementException();
			}
		}
	}

	private static class Printer extends PrintWriter {
		Printer(PrintStream out) {
			super(out);
		}
	}
}


Measured memory_bytes: 23380