#include<iostream>
#include<math.h>

using namespace std;
typedef pair<int, int> pii;
int W, H, ans=999;
char fld[20][20];
int tag[20][20];

bool is_fld(int h, int w){
    return (0<=h&&h<H&&0<=w&&w<W);
}

void dfs(int h, int w, int id){
    if(!is_fld(h, w)) return;
    if(fld[h][w]=='#') return;
    if(tag[h][w]!=-1) return;
    tag[h][w]=id;
    const pii dd[]={{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
    for(auto d: dd){
        dfs(h+d.first, w+d.second, id);
    }
    return;
}

int dist(int a, int b, int c, int d){
    return (abs(a-c)+abs(b-d)-1);
}

void solve(){

    int id=1;
    for(int i=0; i<H; i++){
        for(int j=0; j<W; j++){
            if(fld[i][j]=='#') continue;
            if(tag[i][j]!=-1) continue;
            dfs(i, j, id);
            id++;
        }
    }

    for(int i1=0; i1<H; i1++){
        for(int j1=0; j1<W; j1++){
            if(fld[i1][j1]=='#') continue;
            for(int i2=0; i2<H; i2++){
                for(int j2=0; j2<W; j2++){
                    if(fld[i2][j2]=='#') continue;
                    if((tag[i1][j1]==1)&&(tag[i2][j2]==2)){
                        ans=min(ans, dist(i1, j1, i2, j2));
                    }
                }
            }
        }
    }
    return;
}

int main(){

    cin>> W>> H;
    for(int i=0; i<H; i++){
        for(int j=0; j<W; j++){
            cin>> fld[i][j];
        }
    }

    fill(tag[0], tag[20], -1);
    solve();

    cout<< ans<< endl;

    return 0;
}