text: #pragma comment(linker, "/stack:640000000")
  
  #include <algorithm>
  #include <bitset>
  #include <cassert>
  #include <cctype>
  #include <climits>
  #include <cmath>
  #include <cstdio>
  #include <cstdlib>
  #include <cstring>
  #include <fstream>
  #include <iostream>
  #include <iomanip>
  #include <iterator>
  #include <list>
  #include <map>
  #include <numeric>
  #include <queue>
  #include <set>
  #include <sstream>
  #include <stack>
  #include <string>
  #include <utility>
  #include <vector>
  using namespace std;
  
  const double EPS = 1e-9;
  const int INF = 0x7f7f7f7f;
  const double PI=acos(-1.0);
  
  #define    READ(f) 	         freopen(f, "r", stdin)
  #define    WRITE(f)   	     freopen(f, "w", stdout)
  #define    MP(x, y) 	     make_pair(x, y)
  #define    PB(x)             push_back(x)
  #define    rep(i,n)          for(int i = 1 ; i<=(n) ; i++)
  #define    repI(i,n)         for(int i = 0 ; i<(n) ; i++)
  #define    FOR(i,L,R) 	     for (int i = L; i <= R; i++)
  #define    ROF(i,L,R) 	     for (int i = L; i >= R; i--)
  #define    FOREACH(i,t)      for (typeof(t.begin()) i=t.begin(); i!=t.end(); i++)
  #define    ALL(p) 	         p.begin(),p.end()
  #define    ALLR(p) 	         p.rbegin(),p.rend()
  #define    SET(p) 	         memset(p, -1, sizeof(p))
  #define    CLR(p)            memset(p, 0, sizeof(p))
  #define    MEM(p, v)         memset(p, v, sizeof(p))
  #define    getI(a) 	         scanf("%d", &a)
  #define    getII(a,b) 	     scanf("%d%d", &a, &b)
  #define    getIII(a,b,c)     scanf("%d%d%d", &a, &b, &c)
  #define    getL(a)           scanf("%lld",&a)
  #define    getLL(a,b)        scanf("%lld%lld",&a,&b)
  #define    getLLL(a,b,c)     scanf("%lld%lld%lld",&a,&b,&c)
  #define    getC(n)           scanf("%c",&n)
  #define    getF(n)           scanf("%lf",&n)
  #define    getS(n)           scanf("%s",n)
  #define    bitCheck(N,in)    ((bool)(a&(1<<(k))))
  #define    bitOff(N,in)      (a&(~(1<<(k))))
  #define    bitOn(N,in)       (a|(1<<(k)))
  #define    iseq(a,b)          (fabs(a-b)<EPS)
  #define    iseq(a,b)          (fabs(a-b)<EPS)
  #define    vi 	 vector < int >
  #define    vii 	 vector < vector < int > >
  #define    pii 	 pair< int, int >
  #define    ff 	 first
  #define    ss 	 second
  #define    ll	 long long
  #define    ull 	 unsigned long long
  
  template< class T > inline T _abs(T n) { return ((n) < 0 ? -(n) : (n)); }
  template< class T > inline T _max(T a, T b) { return (!((a)<(b))?(a):(b)); }
  template< class T > inline T _min(T a, T b) { return (((a)<(b))?(a):(b)); }
  template< class T > inline T _swap(T &a, T &b) { a=a^b;b=a^b;a=a^b;}
  template< class T > inline T gcd(T a, T b) { return (b) == 0 ? (a) : gcd((b), ((a) % (b))); }
  template< class T > inline T lcm(T a, T b) { return ((a) / gcd((a), (b)) * (b)); }
  template <typename T> string NumberToString ( T Number ) { ostringstream ss; ss << Number; return ss.str(); }
  
  #ifdef dipta007
       #define debug(args...) {cerr<<"Debug: "; dbg,args; cerr<<endl;}
  #else
      #define debug(args...)  // Just strip off all debug tokens
  #endif
  
  struct debugger{
      template<typename T> debugger& operator , (const T& v){
          cerr<<v<<" ";
          return *this;
      }
  }dbg;
  
  vii adjlist;
  int visited[10004];
  stack <int> s;
  
  void dfs(int u)
  {
      visited[u]=1;
      FOR(i,0,(int)adjlist[u].size()-1)
      {
          int v = adjlist[u][i];
          if(visited[v]==0) dfs(v);
      }
      s.push(u);
  }
  
  void dfs2(int u)
  {
      visited[u]=1;
      FOR(i,0,(int)adjlist[u].size()-1)
      {
          int v = adjlist[u][i];
          if(visited[v]==0) dfs(v);
      }
  }
  
  int main() {
      #ifdef dipta007
          READ("in.txt");
          //WRITE("out.txt");
      #endif // dipta007
  
      int t;
      getI(t);
      FOR(ci,1,t)
      {
          int n,m;
          getII(n,m);
          adjlist.assign(n+4,vi());
          FOR(i,1,m)
          {
              int a,b;
              getII(a,b);
              adjlist[a].PB(b);
          }
          CLR(visited);
          FOR(i,1,n)
          {
              if(visited[i]==0) dfs(i);
          }
          CLR(visited);
          int cnt=0;
          while(!s.empty())
          {
              if(visited[s.top()]==0)
              {
                  dfs2(s.top());
                  cnt++;
              }
              s.pop();
          }
          printf("Case %d: %d\n",ci,cnt);
      }
  
      return 0;
  }
  
  
  
  