#include <cstdio>

#include <cstring>

#include <cmath>

#include <iostream>

#include <algorithm>

#include <queue>

#include <cstdlib>

#include <vector>

#include <set>

#include <map>

#define LL long long

#define mod 1000000007

#define inf 0x3f3f3f3f

#define N 100010

using namespace std;

struct node

{

    int x,y,step;

};

int vis[][],n,m;

char s[][];

int px[],py[],tot;

int dx[]={,,,-};

int dy[]={,-,,};

queue<node>que;

node make_node(int a,int b,int c)

{

    node temp;

    temp.x=a;temp.y=b;temp.step=c;

    return temp;

}

bool judge(int x,int y)

{

    return x>=&&x<=n&&y>=&&y<=m&&s[x][y]=='#'&&!vis[x][y];

}

int bfs(int i,int j)

{

    memset(vis,,sizeof(vis));

    while(!que.empty())que.pop();

    que.push(make_node(px[i],py[i],));

    que.push(make_node(px[j],py[j],));

    vis[px[i]][py[i]]=;vis[px[j]][py[j]]=;

    int sum=,mx=;

    while(!que.empty())

    {

        node cur,nxt;

        cur=que.front();que.pop();

        int step=cur.step;

        mx=max(step,mx);

        sum++;

        for(int ii=;ii<;ii++)

        {

            int x=dx[ii]+cur.x,y=dy[ii]+cur.y;

            if(judge(x,y))

            {

                vis[x][y]=;

                que.push(make_node(x,y,step+));

            }

        }

    }

    if(sum==tot)return mx;

    else return inf;

}

int main()

{

    int T,cas=;

    scanf("%d",&T);

    while(T--)

    {

        scanf("%d%d",&n,&m);

        for(int i=;i<=n;i++)scanf("%s",s[i]+);

        tot=;

        for(int i=;i<=n;i++)

        {

            for(int j=;j<=m;j++)

                if(s[i][j]=='#')

                {

                    px[++tot]=i;py[tot]=j;

                }

        }

        printf("Case %d: ",cas++);

        if(tot<=)

        {

            puts("");continue;

        }

        int ans=inf;

        for(int i=;i<=tot;i++)

        for(int j=i+;j<=tot;j++)

        {

            ans=min(ans,bfs(i,j));

        }

        if(ans==inf)puts("-1");

        else printf("%d\n",ans);

    }

}