#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <queue>

using namespace std;
using ull = unsigned long long;
using ll = long long;
using lli = long long int;
using ld = long double;
using pa = pair<int,int>;
#define SORT(v, n) sort(v, v+n);
#define VSORT(v) sort(v.begin(), v.end());
#define GRESORT(v) sort(v.begin(),v.end(),greater<int>())
#define REVERSE(v) reverse(v.begin(),v.end())
#define overlap(v) v.erase(unique(v.begin(),v.end()),v.end())
#define debug(x) cout << #x << ": " << x << endl
#define FOR(i,a,b) for(int i = (a); i < (b); i++)
#define rep(i,n) FOR(i,0,n)
#define RFOR(i,a,b) for(int i = (b-1); i >= a; i--)
#define rrep(i,n) RFOR(i,0,n)
#define INF 999999999

//4近傍
int dy[]={0, 0, 1, -1};
int dx[]={1, -1, 0, 0};

//8近傍
//int dy[]={0,0,1,-1,1,1,-1,-1};
//int dx[]={1,-1,0,0,1,-1,1,-1};

lli mod = (lli)1e9+7;

void solve(){
    int w,h; cin >> w >> h;
    vector<string> s(h);
    rep(i,h) cin >> s[i];

    int sy,sx;
    rep(i,h){
        rep(j,w){
            if(s[i][j] == '.'){
                sy = i; sx = j; i = h; j = w;
            }
        }
    }

    vector<vector<int>> d(h,vector<int>(w));
    rep(i,h) rep(j,w) d[i][j] = INF;

    queue<pa> q;
    q.push(pa(sx,sy));

    d[sy][sx] = 0;

    queue<pa> hoge;
    hoge.push(pa(sx,sy));

    while(!q.empty()){
        pa p = q.front(); q.pop();
        int x = p.first, y = p.second;
        rep(i,4){
            int xx = x + dx[i];
            int yy = y + dy[i];
            if(xx < 0 || yy < 0 || xx >= w || yy >= h) continue;
            if(d[yy][xx] == INF && s[yy][xx] == '.'){
                q.push(pa(xx,yy));
                hoge.push(pa(xx,yy));
                d[yy][xx] = 0;
            }
        }
    }


    while(!hoge.empty()){
        pa p = hoge.front(); hoge.pop();
        int x = p.first, y = p.second;
        rep(i,4){
            int xx = x + dx[i];
            int yy = y + dy[i];
            if(xx < 0 || yy < 0 || xx >= w || yy >= h) continue;
            if(d[yy][xx] == 0) continue;
            if(s[yy][xx] == '#' && d[yy][xx] > d[y][x] + 1){
                d[yy][xx] = d[y][x]+1;
                hoge.push(pa(xx,yy));
            }
        }
    }

    int ans = INF;
    rep(i,h){
        rep(j,w){
            if(d[i][j] == INF){
                rep(k,4){
                    ans = min(ans,d[i+dx[k]][j+dy[k]]);
                }
            }
        }
    }

    cout << ans << endl;
}

int main(){
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);

    solve();

    return 0;
}