import java.io.InputStream;
import java.io.PrintStream;
import java.util.ArrayDeque;
import java.util.Arrays;
import java.util.List;
import java.util.Queue;
import java.util.Scanner;

public class Main {
	InputStream in = System.in;
	PrintStream out = System.out;

	public void _main(String[] args) {
		Scanner sc = new Scanner(in);

		int H = sc.nextInt();
		int W = sc.nextInt();
		char[][] s = new char[H][W];
		
		int a = 0;
		for(int i=0;i<H;i++) {
			String l = sc.next();
			for(int j=0;j<W;j++) {
				s[i][j] = l.charAt(j);
				if(s[i][j] == '#') a++;
			}
		}
		
		sc.close();

		Queue<List<Integer>> q = new ArrayDeque<>();
		q.add(Arrays.asList(0,0));
		
		int[][] m = new int[H][W];
		m[0][0] = 1;
		
		int[] dw = {0, 1, 0, -1 };
		int[] dh = {-1, 0, 1, 0 };
		
		while(!q.isEmpty()) {
			List<Integer> l = q.poll();
			int h = l.get(0);
			int w = l.get(1);
			
			if(h==H-1 && w==W-1) {
				break;
			}
			for(int i=0;i<4;i++) {
				int nh = h+dh[i];
				int nw = w+dw[i];
				
				if(nh>=0 && nh<H && nw>=0 && nw<W && m[nh][nw] == 0 && s[nh][nw] == '.') {
					
					m[nh][nw] = m[h][w] + 1;
					q.add(Arrays.asList(nh, nw));
				}
			}
			
		}
		
		if(m[H-1][W-1] == 0) {
			out.println(-1);
		}else {
			out.println(H*W-a -m[H-1][W-1]);
		}
	}

	public static void main(String[] args) {
		new Main()._main(args);
	}

	@SuppressWarnings("unused")
	private String join(String delimiter, int[] a) {
		StringBuilder sb = new StringBuilder();

		for (int i = 0; i < a.length; i++) {
			sb.append(a[i]);
			sb.append(delimiter);
		}
		return sb.substring(0, Math.max(sb.length() - delimiter.length(), 0));
	}

	@SuppressWarnings("unused")
	private String join(String delimiter, long[] a) {
		StringBuilder sb = new StringBuilder();

		for (int i = 0; i < a.length; i++) {
			sb.append(a[i]);
			sb.append(delimiter);
		}
		return sb.substring(0, Math.max(sb.length() - delimiter.length(), 0));
	}

	@SuppressWarnings("unused")
	private int max(int[] arr) {
		if(arr == null || arr.length == 0) {
			throw new IllegalArgumentException(Arrays.toString(arr));
		}

		int candidate = arr[0];
		for(int i=1;i<arr.length;i++) {
			candidate = candidate > arr[i] ? candidate : arr[i];
		}
		return candidate;
	}

	@SuppressWarnings("unused")
	private long max(long[] arr) {
		if(arr == null || arr.length == 0) {
			throw new IllegalArgumentException(Arrays.toString(arr));
		}

		long candidate = arr[0];
		for(int i=1;i<arr.length;i++) {
			candidate = candidate > arr[i] ? candidate : arr[i];
		}
		return candidate;
	}

	@SuppressWarnings("unused")
	private int min(int[] arr) {
		if(arr == null || arr.length == 0) {
			throw new IllegalArgumentException(Arrays.toString(arr));
		}

		int candidate = arr[0];
		for(int i=1;i<arr.length;i++) {
			candidate = candidate < arr[i] ? candidate : arr[i];
		}
		return candidate;
	}

	@SuppressWarnings("unused")
	private long min(long[] arr) {
		if(arr == null || arr.length == 0) {
			throw new IllegalArgumentException(Arrays.toString(arr));
		}

		long candidate = arr[0];
		for(int i=1;i<arr.length;i++) {
			candidate = candidate < arr[i] ? candidate : arr[i];
		}
		return candidate;
	}

	@SuppressWarnings("unused")
	private int[] nextIntArray(Scanner sc, int n) {
		int[] result = new int[n];
		for (int i = 0; i < n; i++) {
			result[i] = sc.nextInt();
		}
		return result;
	}

	@SuppressWarnings("unused")
	private long[] nextLongArray(Scanner sc, int n) {
		long[] result = new long[n];
		for (int i = 0; i < n; i++) {
			result[i] = sc.nextLong();
		}
		return result;
	}

	@SuppressWarnings("unused")
	private int[] nextIntArray1origin(Scanner sc, int n) {
		int[] result = new int[n + 1];
		for (int i = 1; i <= n; i++) {
			result[i] = sc.nextInt();
		}
		return result;
	}
}


Measured memory_bytes: 23380