Problem:
Score: 400 points

Problem statement

We have an H \times W grid whose squares are painted black or white. The square at the i-th row from the top and the j-th column from the left is denoted as (i, j).

Snuke would like to play the following game on this grid. At the beginning of the game, there is a character called Kenus at square (1, 1). The player repeatedly moves Kenus up, down, left or right by one square. The game is completed when Kenus reaches square (H, W) passing only white squares.

Before Snuke starts the game, he can change the color of some of the white squares to black. However, he cannot change the color of square (1, 1) and (H, W). Also, changes of color must all be carried out before the beginning of the game.

When the game is completed, Snuke's score will be the number of times he changed the color of a square before the beginning of the game. Find the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed, that is, Kenus can never reach square (H, W) regardless of how Snuke changes the color of the squares.

The color of the squares are given to you as characters s_{i, j}. If square (i, j) is initially painted by white, s_{i, j} is .; if square (i, j) is initially painted by black, s_{i, j} is #.

Constraints

H is an integer between 2 and 50 (inclusive).

W is an integer between 2 and 50 (inclusive).

s_{i, j} is . or # (1 \leq i \leq H, 1 \leq j \leq W).

s_{1, 1} and s_{H, W} are ..

Input

Input is given from Standard Input in the following format:

H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
: :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}

Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Sample Input 1

3 3
..#
#..
...

Sample Output 1

2

The score 2 can be achieved by changing the color of squares as follows:

Sample Input 2

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................

Sample Output 2

209

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.text.DecimalFormat;
import java.util.ArrayDeque;
import java.util.Arrays;


 
 
public class Main {
	
	public static void main(String[] args) throws IOException {
		Main m = new Main();
		//*
		m.input();
		m.solve();
		m.output();
		/*/
		m.debug();
		//*/
	}
	
	public void debug() {
	}
	
	//*
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	String S = null;
	/*/
	InputUtil in = new InputUtil();
	//*/
	PrintWriter out = new PrintWriter(System.out);
	int H = 0;
	int W = 0;
	char[][] buf = null;
	int[][] step = null;
	int countWall = 0;
	int ans = -1;
	
	
	
	
	public void input() throws IOException {
		String[] tmpStrs = br.readLine().split(" ");
		H = Integer.parseInt(tmpStrs[0]);
		W = Integer.parseInt(tmpStrs[1]);
		buf = new char[H+2][W+2];
		step = new int[H+2][W+2];
		Arrays.fill(buf[0], '#');
		Arrays.fill(step[0], Integer.MAX_VALUE);
		for(int i=1; i<H+1; i++) {
			String tmpStr = br.readLine();
			if (tmpStr == null) {
				break;
			}
			char[] tmpAry = tmpStr.toCharArray();
			for (char c: tmpAry) {
				if (c == '#') {
					countWall ++;
				}
			}
			Arrays.fill(buf[i], '#');
			Arrays.fill(step[i], Integer.MAX_VALUE);
			System.arraycopy(tmpAry, 0, buf[i], 1, tmpAry.length);
		}
		Arrays.fill(buf[H+1], '#');
		Arrays.fill(step[H+1], Integer.MAX_VALUE);
		step[1][1]=1;

	}
//	
//	private void debugOutput() {
//		DecimalFormat df = new DecimalFormat("00");
//		for (int y=0; y<H+2; y++) {
//			System.out.println(buf[y]);
//		}
//		for (int y=0; y<H+2; y++) {
//			for (int x=0; x<W+2; x++) {
//				if (x>0) {
//					System.out.print(",");
//				}
//				if (step[y][x] < Integer.MAX_VALUE) {
//					System.out.print(df.format(step[y][x]));
//				} else { 
//					System.out.print("##");
//				}
//			}
//			System.out.println("");
//		}
//	}
	
	public void solve() throws IOException {
		ArrayDeque<Point> q = new ArrayDeque<Point>();
		Point[] dirs = new Point[4];
		dirs[0] = new Point(1,0);
		dirs[1] = new Point(0,1);
		dirs[2] = new Point(-1,0);
		dirs[3] = new Point(0,-1);
		q.add(new Point(1,1));
		while (!q.isEmpty()) {
			Point p = q.poll();
			for (int dir=0; dir<dirs.length; dir++) {
				Point d = dirs[dir];
				Point np = p.move(d);
				if (buf[np.y][np.x]=='.' && step[np.y][np.x] > step[p.y][p.x] + 1) {
					step[np.y][np.x] = step[p.y][p.x] + 1;
					q.add(np);
				}
//				System.out.println("-----------p=("+p.y+","+p.x+"), d=("+d.y+","+d.x+"), np="+np.y+","+np.x+"");
//				debugOutput();
			}
		}
		if (step[H][W] == Integer.MAX_VALUE) {
			ans = -1;
		} else {
			ans = (H*W) - countWall - step[H][W];
		}
			
	}

	
	public void output() {
		out.println(ans);
		out.flush();
	}
}

class Point {
	int y;
	int x;
	public Point(int y, int x) {
		this.x=x;
		this.y=y;
	}
	
	public Point move(Point d) {
		Point p = new Point(y, x);
		p.x += d.x;
		p.y += d.y;
		return p;
	}
	
}

/*
class InputUtil {
	//Static Fields
	private static final int BUFSIZ = 100000;
	
	//Fields
	protected InputStream in;
	private byte[] buf = null;
	private int ptr = 0;
	private int max = -1;
	private DataInputStream dis = null;
	//Constructors
	public InputUtil() {this(System.in,BUFSIZ);}
	public InputUtil(InputStream in, int bufsiz) {
		initBuf(bufsiz);
		initIn(in);
	}
	
	//Methods
	//Initializer
	protected void initIn(InputStream in) {dis = new DataInputStream(this.in = in);}
	protected void initBuf(int bufsiz) {buf = new byte[bufsiz];}
	
	//buffer operation
	private void next() throws IOException {ptr++; readBuf();}
	private void readBuf() throws IOException {
		if(ptr >= max && dis.available()>0) {
			if(max>0) Arrays.fill(buf,0,max,(byte)0);
			max = dis.read(buf);
			ptr = 0;
		}
	}
	
	//Number Input Reader/Parser
	private boolean isNum(byte b) {return '0' <= b && b <= '9'; }
	private boolean isMinus(byte b) {return b=='-'; }
 
	private long _nextLong() throws IOException {
		int sign = 1;
		long res = 0;
		byte c;
		while (!isNum(c=buf[ptr]) && !isMinus(c)) 
			next();
		if (isMinus(buf[ptr])) {
			sign = -1;
			next();
		}
		while (isNum(c=buf[ptr])) {
			res *= 10;
			res += c - '0' ;
			next();
		}
		next();
		return sign * res;
	}
	
	public long nextLong() throws IOException {
		readBuf();
		return _nextLong();
	}
 
	public long[] nextLong(long[] result) throws IOException {
		readBuf();
		for(int i=0; i<result.length; i++) {
			result[i] = _nextLong();
		}
		return result;
	}
	
	//Close 
	public void close() throws IOException {
		if(!this.in.equals(System.in)) 
			this.in.close();
	}
}
//*/