You've gotten an n × m sheet of squared paper. Some of its squares are painted. Let's mark the set of all painted squares as A. Set A is connected. Your task is to find the minimum number of squares that we can delete from set A to make it not connected.

A set of painted squares is called connected, if for every two squares a and b from this set there is a sequence of squares from the set, beginning in a and ending in b, such that in this sequence any square, except for the last one, shares a common side with the square that follows next in the sequence. An empty set and a set consisting of exactly one square are connected by definition.

Input

The first input line contains two space-separated integers n and m (1 ≤ n, m ≤ 50) — the sizes of the sheet of paper. 

Each of the next n lines contains m characters — the description of the sheet of paper: the j-th character of the i-th line equals either "#", if the corresponding square is painted (belongs to set A), or equals "." if the corresponding square is not painted (does not belong to set A). It is guaranteed that the set of all painted squares A is connected and isn't empty.

Output

On the first line print the minimum number of squares that need to be deleted to make set A not connected. If it is impossible, print -1. 

Examples

Input

5 4
####
#..#
#..#
#..#
####


Output

2


Input

5 5
#####
#...#
#####
#...#
#####


Output

2

Note

In the first sample you can delete any two squares that do not share a side. After that the set of painted squares is not connected anymore.

The note to the second sample is shown on the figure below. To the left there is a picture of the initial set of squares. To the right there is a set with deleted squares. The deleted squares are marked with crosses. 

<image>
/* Codeforces Template */

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

import static java.lang.Math.*;
import static java.util.Arrays.fill;
import static java.util.Arrays.binarySearch;
import static java.util.Arrays.sort;

public class Main {
	
	static long initTime;
	static final Random rnd = new Random(7777L);
	
	public static void main(String[] args) throws IOException {
		initTime = System.currentTimeMillis();
		new Thread(null, new Runnable() {
			public void run() {
				try {
					try {
						if (new File("input.txt").exists())
							System.setIn(new FileInputStream("input.txt"));
					} catch (SecurityException e) {}
//					long prevTime = System.currentTimeMillis();
					new Main().run();
//					System.err.println("Total time: " + (System.currentTimeMillis() - prevTime) + " ms");
//					System.err.println("Memory status: " + memoryStatus());
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}, "1", 1L << 24).start(); 
	}

	void run() throws IOException {
		in = new BufferedReader(new InputStreamReader(System.in));
		out = new PrintWriter(System.out);
		solve();
		out.close();
		in.close();
	}
	
	/*************************************************************** 
	 * Solution
	 **************************************************************/

	int n;
	int m;
	char[][] map;
	
	int[][] used;
	int tick;
	
	int[] dr = { -1, 0, 1, 0 };
	int[] dc = { 0, -1, 0, 1 };
	
	void solve() throws IOException  {
		
		n = nextInt();
		m = nextInt();
		map = new char [n][];
		
		for (int i = 0; i < n; i++) {
			map[i] = nextToken().toCharArray();
		}
		
		int cnt = 0;
		
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < m; j++) {
				cnt += map[i][j] == '#' ? 1 : 0;
			}
		}
		
		if (cnt <= 2) {
			out.println("-1");
			return;
		}
		
		int ans = 100;
		
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < m; j++) {
				if (map[i][j] == '#') {
					int cur = 0;
					cur += get(map, i - 1, j);
					cur += get(map, i + 1, j);
					cur += get(map, i, j - 1);
					cur += get(map, i, j + 1);
					ans = min(ans, cur);
				}
			}
		}
		
		used = new int [n][m];
		
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < m; j++) {
				if (map[i][j] == '#') {
					map[i][j] = '.';
					
					
					for (int d = 0; d < 4; d++) {
						int nr = i + dr[d];
						int nc = j + dc[d];
						if (get(map, nr, nc) == 1) {
							tick++;
							if (dfs(nr, nc) + 1 != cnt) {
								out.println(1);
								return;
							}
							break;
						}
					}
					
					map[i][j] = '#';
				}
			}
		}
		
		out.println(ans);
		
	}
	
	int dfs(int r, int c) {
		used[r][c] = tick;
		
		int ret = 1;
		
		for (int d = 0; d < 4; d++) {
			int nr = r + dr[d];
			int nc = c + dc[d];
			if (get(map, nr, nc) == 1 && used[nr][nc] != tick) {
				ret += dfs(nr, nc);
			}
		}
		
		return ret;
	}

	int get(char[][] map, int i, int j) {
		if (0 <= i && i < n && 0 <= j && j < m)
			return map[i][j] == '#' ? 1 : 0;
		return 0;
	}

	/*************************************************************** 
	 * Input 
	 **************************************************************/
	BufferedReader in;
	PrintWriter out;
	StringTokenizer st = new StringTokenizer("");
	
	String nextToken() throws IOException {
		while (!st.hasMoreTokens())
			st = new StringTokenizer(in.readLine());
		return st.nextToken();
	}
	
	int nextInt() throws IOException {
		return Integer.parseInt(nextToken());
	}
	
	long nextLong() throws IOException {
		return Long.parseLong(nextToken());
	}
	
	double nextDouble() throws IOException {
		return Double.parseDouble(nextToken());
	}
	
	int[] nextIntArray(int size) throws IOException {
		int[] ret = new int [size];
		for (int i = 0; i < size; i++)
			ret[i] = nextInt();
		return ret;
	}
	
	long[] nextLongArray(int size) throws IOException {
		long[] ret = new long [size];
		for (int i = 0; i < size; i++)
			ret[i] = nextLong();
		return ret;
	}
	
	double[] nextDoubleArray(int size) throws IOException {
		double[] ret = new double [size];
		for (int i = 0; i < size; i++)
			ret[i] = nextDouble();
		return ret;
	}
	
	String nextLine() throws IOException {
		st = new StringTokenizer("");
		return in.readLine();
	}
	
	boolean EOF() throws IOException {
		while (!st.hasMoreTokens()) {
			String s = in.readLine();
			if (s == null)
				return true;
			st = new StringTokenizer(s);
		}
		return false;
	}
	
	/*************************************************************** 
	 * Output 
	 **************************************************************/
	void printRepeat(String s, int count) {
		for (int i = 0; i < count; i++)
			out.print(s);
	}
	
	void printArray(int[] array) {
		if (array == null || array.length == 0)
			return;
		for (int i = 0; i < array.length; i++) {
			if (i > 0) out.print(' ');
			out.print(array[i]);
		}
		out.println();
	}
	
	void printArray(long[] array) {
		if (array == null || array.length == 0)
			return;
		for (int i = 0; i < array.length; i++) {
			if (i > 0) out.print(' ');
			out.print(array[i]);
		}
		out.println();
	}
	
	void printArray(double[] array) {
		if (array == null || array.length == 0)
			return;
		for (int i = 0; i < array.length; i++) {
			if (i > 0) out.print(' ');
			out.print(array[i]);
		}
		out.println();
	}
	
	void printArray(double[] array, String spec) {
		if (array == null || array.length == 0)
			return;
		for (int i = 0; i < array.length; i++) {
			if (i > 0) out.print(' ');
			out.printf(Locale.US, spec, array[i]);
		}
		out.println();
	}
	
	void printArray(Object[] array) {
		if (array == null || array.length == 0)
			return;
		boolean blank = false;
		for (Object x : array) {
			if (blank) out.print(' '); else blank = true;
			out.print(x);
		}
		out.println();
	}
	
	@SuppressWarnings("rawtypes")
	void printCollection(Collection collection) {
		if (collection == null || collection.isEmpty())
			return;
		boolean blank = false;
		for (Object x : collection) {
			if (blank) out.print(' '); else blank = true;
			out.print(x);
		}
		out.println();
	}
	
	/*************************************************************** 
	 * Utility
	 **************************************************************/
	static String memoryStatus() {
		return (Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory() >> 20) + "/" + (Runtime.getRuntime().totalMemory() >> 20) + " MB";
	}
	
	static void checkMemory() {
		System.err.println(memoryStatus());
	}
	
	static long prevTimeStamp = Long.MIN_VALUE;
	
	static void updateTimer() {
		prevTimeStamp = System.currentTimeMillis();
	}
	
	static long elapsedTime() {
		return (System.currentTimeMillis() - prevTimeStamp);
	}
	
	static void checkTimer() {
		System.err.println(elapsedTime() + " ms");
	}
}
