#include <iostream>
#include <string>
#include <math.h>
#include <vector>
using namespace std;

const int MAX_W = 20;
const int MAX_H = 20;
int W,H;
int ap=0,bp=0;
vector<string> field;
int Ax[MAX_W*MAX_H],Ay[MAX_W*MAX_H],Bx[MAX_W*MAX_H],By[MAX_W*MAX_H];
int dy[] = {1, 0, -1, 0};
int dx[] = { 0, 1, 0, -1 };

void dsf(int x,int y,int count)
{   
    if(count==0) 
    {
        field[x][y] = 'A';
        Ax[ap] = x, Ay[ap] = y;
        ap++;
    }
    else 
    {
        field[x][y] = 'B';
        Bx[bp] = x, By[bp] = y;
        bp++;
    }
    for(int i=0;i<4;i++)
    {   
        int nx = x + dx[i], ny = y + dy[i];
        if (0 <= nx && nx < H && 0 <= ny && ny < W && field[nx][ny]=='.')
        {
            dsf(nx,ny,count);
        }
    }
    return ;
}
void solve()
{
    int min = W*H;
    int d;
    int count = 0;
    for(int h=0;h<H;h++)
    {
        for(int w=0;w<W;w++)
        {
            if(field[h][w]=='.')
            {  
                dsf(h,w,count);
                count++;
            }
            
        }
    }
    for(int i=0;i<ap;i++)
    {
        for(int j=0;j<bp;j++)
        {   
            d = abs(Ax[i]-Bx[j])+abs(Ay[i]-By[j])-1;
            if(d<min)
            {
                min = d;
            }
        }
    }
    cout << min << endl;
}

int main()
{
    cin >> W >> H;
	for(int i=0;i<H;i++)
    {
        string tmp;
        cin >> tmp;
        field.push_back(tmp);
	}
    solve();
    //for(int i=0;i<H;i++)
    //{
    //    cout << field[i] << endl;
    //}
    return 0;
}