Problem Link : http://www.lightoj.com/volume_showproblem.php?problem=1406

/*
         +-+ +-+ +-+
         |R| |.| |S|
         +-+ +-+ +-+
 */

#include <bits/stdc++.h>

#define pii             pair <int,int>
#define sc              scanf
#define pf              printf
#define Pi              2*acos(0.0)
#define ms(a,b)         memset(a, b, sizeof(a))
#define pb(a)           push_back(a)
#define MP              make_pair
#define db              double
#define ll              long long
#define EPS             10E-10
#define ff              first
#define ss              second
#define sqr(x)          (x)*(x)
#define D(x)            cout<<#x " = "<<(x)<<endl
#define VI              vector <int>
#define DBG             pf("Hi\n")
#define MOD             100007
#define MAX             10000
#define CIN             ios_base::sync_with_stdio(0); cin.tie(0)
#define SZ(a)           (int)a.size()
#define sf(a)           scanf("%d",&a)
#define sff(a,b)        scanf("%d%d",&a,&b)
#define sfff(a,b,c)     scanf("%d%d%d",&a,&b,&c)
#define loop(i,n)       for(int i=0;i<n;i++)
#define REP(i,a,b)      for(int i=a;i<b;i++)
#define TEST_CASE(t)    for(int z=1;z<=t;z++)
#define PRINT_CASE      printf("Case %d: ",z)
#define all(a)          a.begin(),a.end()
#define intlim          2147483648
#define inf             1000000
#define ull             unsigned long long


using namespace std;

vector<int>graph[16];
bool visited[16][1<<16];
bool check_vis[1<<16];
int dp[1<<16];
int n,m;

void dfs(int u, int mask)
{
    visited[u][mask]=1;
    check_vis[mask]=1;
    loop(i,SZ(graph[u]))
    {
        int v=graph[u][i];
        if(!visited[v][mask|(1<<v)])
            dfs(v,mask|(1<<v));
    }
}

void allclear()
{
    loop(i,n+1)
    {
        graph[i].clear();
    }
    ms(visited,0);
    ms(check_vis,0);
    ms(dp,-1);
}

int dp_func(int mask)
{
    int &ret = dp[mask];
    if(mask==0) return 0;
    if(ret!=-1) return ret;
    ret=100;
    for(int i=mask; i>0; i=mask & (i-1))
    {
        if(check_vis[i])
        {
            ret=min(ret,1+dp_func(mask^i)); // XOR for remaining unvisited node
        }
    }
    return ret;
}

int main()
{
    ///freopen("in.txt","r",stdin);
   ///freopen("out.txt","w",stdout);
    int t,a,b;
    sf(t);
    TEST_CASE(t)
    {
        sff(n,m);
        allclear();
        loop(i,m)
        {
            sff(a,b);
            a--,b--;
            graph[a].pb(b);
        }

        loop(i,n)
        {
            dfs(i,1<<i);
        }
        PRINT_CASE;
        cout<<dp_func((1<<n)-1)<<endl;
    }
    return 0;
}