//STATUS:C++_AC_46MS_3488KB

 #include <functional>

 #include <algorithm>

 #include <iostream>

 //#include <ext/rope>

 #include <fstream>

 #include <sstream>

 #include <iomanip>

 #include <numeric>

 #include <cstring>

 #include <cassert>

 #include <cstdio>

 #include <string>

 #include <vector>

 #include <bitset>

 #include <queue>

 #include <stack>

 #include <cmath>

 #include <ctime>

 #include <list>

 #include <set>

 #include <map>

 using namespace std;

 //#pragma comment(linker,"/STACK:102400000,102400000")

 //using namespace __gnu_cxx;

 //define

 #define pii pair<int,int>

 #define mem(a,b) memset(a,b,sizeof(a))

 #define lson l,mid,rt<<1

 #define rson mid+1,r,rt<<1|1

 #define PI acos(-1.0)

 //typedef

 typedef __int64 LL;

 typedef unsigned __int64 ULL;

 //const

 const int N=;

 const int INF=0x3f3f3f3f;

 const int MOD=,STA=;

 const LL LNF=1LL<<;

 const double EPS=1e-;

 const double OO=1e15;

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

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

 const int day[]={,,,,,,,,,,,,};

 //Daily Use ...

 inline int sign(double x){return (x>EPS)-(x<-EPS);}

 template<class T> T gcd(T a,T b){return b?gcd(b,a%b):a;}

 template<class T> T lcm(T a,T b){return a/gcd(a,b)*b;}

 template<class T> inline T lcm(T a,T b,T d){return a/d*b;}

 template<class T> inline T Min(T a,T b){return a<b?a:b;}

 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,T c){return min(min(a, b),c);}

 template<class T> inline T Max(T a,T b,T c){return max(max(a, b),c);}

 template<class T> inline T Min(T a,T b,T c,T d){return min(min(a, b),min(c,d));}

 template<class T> inline T Max(T a,T b,T c,T d){return max(max(a, b),max(c,d));}

 //End

 struct Edge{

     int u,v;

 }e[N];

 int first[N],next[N],pre[N],sccno[N],low[N];

 int n,mt,dfs_clock,scnt;

 stack<int> s;

 int cntn[N],in[N],out[N];

 int T,m;

 void adde(int a,int b)

 {

     e[mt].u=a;e[mt].v=b;

     next[mt]=first[a],first[a]=mt++;

 }

 void dfs(int u)

 {

     int i,j,v;

     pre[u]=low[u]=++dfs_clock;

     s.push(u);

     for(i=first[u];i!=-;i=next[i]){

         v=e[i].v;

         if(!pre[v]){

             dfs(v);

             low[u]=Min(low[u],low[v]);

         }

         else if(!sccno[v]){    //反向边更新

             low[u]=Min(low[u],low[v]);

         }

     }

     if(low[u]==pre[u]){   //存在强连通分量

         int x=-;

         scnt++;

         while(x!=u){

             x=s.top();s.pop();

             sccno[x]=scnt;

         }

     }

 }

 void find_scc()

 {

     int i;

     mem(pre,);mem(sccno,);

     scnt=dfs_clock=;

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

         if(!pre[i])dfs(i);

     }

 }

 int main(){

  //   freopen("in.txt","r",stdin);

     int ca=,i,j,a,b,cnt;

     LL ans;

     scanf("%d",&T);

     while(T--)

     {

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

         mem(first,-);mt=;

         for(i=;i<m;i++){

             scanf("%d%d",&a,&b);

             adde(a,b);

         }

         find_scc();

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

         if(scnt==){

             printf("-1\n");

             continue;

         }

         mem(cntn,);

         mem(in,);mem(out,);

         for(i=;i<=n;i++)cntn[sccno[i]]++;

         for(i=;i<mt;i++){

             if(sccno[e[i].u]!=sccno[e[i].v]){

                 in[sccno[e[i].v]]++;

                 out[sccno[e[i].u]]++;

             }

         }

         ans=;

         int low=INF;

         for(i=;i<=scnt;i++){

             if(in[i]== || out[i]==){

                 low=Min(low,cntn[i]);

             }

         }

         ans+=(LL)(n-)*n-(LL)low*(n-low)-(LL)m;

         printf("%I64d\n",ans);

     }

     return ;

 }