import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Deque;
import java.util.HashMap;
import java.util.InputMismatchException;
import java.util.Map;
import java.util.PriorityQueue;
import java.math.BigInteger;
    
public class Main{

static final InputStream in=System.in;
static final PrintWriter out=new PrintWriter(System.out);
static final int INF=Integer.MAX_VALUE/2;
static final long LINF=Long.MAX_VALUE/2;
static final int[] dx={1,0,-1,0};
static final int[] dy={0,1,0,-1};
    
public static void main(String[] args) throws IOException{
InputReader ir=new InputReader(in);
int w=ir.nextInt();
int h=ir.nextInt();
int ans=INF;
char[][] map=new char[h][w];
boolean[][] isCave1=new boolean[h][w];
int[][] dist=new int[h][w];
for(int i=0;i<h;i++) map[i]=ir.next().toCharArray();
lo: for(int i=0;i<h;i++){
for(int j=0;j<w;j++){
if(map[i][j]=='.'){
dfs(i,j,map,isCave1,w,h);
break lo;
}
}
}
for(int i=0;i<h;i++){
for(int j=0;j<w;j++){
if(isCave1[i][j]){
for(int k=0;k<4;k++){
int nx=i+dx[k];
int ny=j+dy[k];
if(nx>=0&&nx<h&&ny>=0&&ny<w&&!isCave1[nx][ny]) ans=Math.min(ans,bfs(nx,ny,map,dist,isCave1,w,h));
}
}
}
}
out.println(ans);
out.flush();
}

public static void dfs(int x,int y,char[][] map,boolean[][] isCave1,int w,int h){
isCave1[x][y]=true;
for(int i=0;i<4;i++){
int nx=x+dx[i];
int ny=y+dy[i];
if(nx>=0&&nx<h&&ny>=0&&ny<w&&!isCave1[nx][ny]&&map[nx][ny]=='.') dfs(nx,ny,map,isCave1,w,h);
}
}

public static int bfs(int sx,int sy,char[][] map,int[][] dist,boolean[][] isCave1,int w,int h){
for(int i=0;i<h;i++) Arrays.fill(dist[i],INF);
Deque<Pair> que=new ArrayDeque<Pair>();
dist[sx][sy]=0;
que.offerLast(new Pair(sx,sy));
while(!que.isEmpty()){
Pair p=que.pollFirst();
int x=p.x;
int y=p.y;
for(int i=0;i<4;i++){
int nx=x+dx[i];
int ny=y+dy[i];
if(nx>=0&&nx<h&&ny>=0&&ny<w&&!isCave1[nx][ny]){
if(map[x][y]=='.') return dist[x][y]+1;
if(dist[nx][ny]>dist[x][y]){
que.offerLast(new Pair(nx,ny));
dist[nx][ny]=dist[x][y]+1;
}
}
}
}
return INF;
}

static class Pair{

public static int x;
public static int y;

public Pair(int x,int y){
this.x=x; this.y=y;
}

public static final Comparator<Pair> DISTANCE_ORDER=new Comp();
private static class Comp implements Comparator<Pair>{
public int compare(Pair p1,Pair p2){
return p1.x>p2.x?1:p1.x<p2.x?-1:0;
}
}

public String toString(){return "["+x+","+y+"]";}
}


static class InputReader {

private InputStream in;
private byte[] buffer=new byte[1024];
private int curbuf;
private int lenbuf;

public InputReader(InputStream in) {this.in=in;}
  
public int readByte() {
if(lenbuf==-1) throw new InputMismatchException();
if(curbuf>=lenbuf){
curbuf= 0;
try{
lenbuf=in.read(buffer);
}
catch (IOException e) {
throw new InputMismatchException();
}
if(lenbuf<=0)
return -1;
}
return buffer[curbuf++];
}

public boolean isSpaceChar(int c){return !(c>=33&&c<=126);}

private int skip() {int b; while((b = readByte())!=-1&&isSpaceChar(b)); return b;}

public String next() {
int b=skip();
StringBuilder sb=new StringBuilder();
while(!isSpaceChar(b)){
sb.appendCodePoint(b);
b=readByte();
}
return sb.toString();
}
 
public int nextInt() {
int c=readByte();
while (isSpaceChar(c)) c=readByte();
boolean minus=false;
if (c=='-') {
minus=true;
c=readByte();
}
int res=0;
do{
if(c<'0'||c>'9') throw new InputMismatchException();
res=res*10+c-'0';
c=readByte();
}while(!isSpaceChar(c));
return (minus)?-res:res;
}

public long nextLong() {
int c=readByte();
while (isSpaceChar(c)) c=readByte();
boolean minus=false;
if (c=='-') {
minus=true;
c=readByte();
}
long res = 0;
do{
if(c<'0'||c>'9') throw new InputMismatchException();
res=res*10+c-'0';
c=readByte();
}while(!isSpaceChar(c));
return (minus)?-res:res;
}

public int[] toIntArray(int n){
int[] a=new int[n];
for(int i=0;i<n;i++) a[i]=nextInt();
return a;
}
}
}