#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdio>
#include<bitset>
#include<cmath>
#define LL long long
#define M 1020
using namespace std;
int read(){int nm=0,fh=1; char cw=getchar();for(;!isdigit(cw);cw=getchar()) if(cw=='-') fh=-fh;for(;isdigit(cw);cw=getchar()) nm=nm*10+(cw-'0');return nm*fh;
}
int n,m,c[M][M],sz[M],vis[M],dfn[M],low[M],cnt,S[M],top,tk[M],hd,tl,q[M];
int fs[M],to[M*M],tmp,nt[M*M],be[M],tot,ct[M],ind[M]; bool gt[M][M]; bitset<M>G[M];
void link(int x,int y){nt[tmp]=fs[x],fs[x]=tmp,to[tmp++]=y,ind[y]++;}
void dfs(int x){cnt++,dfn[x]=low[x]=cnt,S[++top]=x,S[top+1]=0;for(int i=1;i<=ct[x];i++){if(!dfn[c[x][i]]) dfs(c[x][i]);if(!be[c[x][i]]) low[x]=min(low[x],low[c[x][i]]);}if(low[x]<dfn[x]) return; sz[++tot]=0,G[tot].reset(),ind[tot]=0;while(S[top+1]!=x) be[S[top]]=tot,sz[tot]++,G[tot].set(S[top]),top--;
}
int main(){for(int tt=1,T=read();tt<=T;tt++){tot=cnt=hd=tl=tmp=0,n=read(),memset(vis,0,sizeof(vis)),memset(dfn,0,sizeof(dfn));memset(fs,-1,sizeof(fs)),memset(gt,false,sizeof(gt)),memset(be,0,sizeof(be));for(int i=1;i<=n;i++) for(ct[i]=0,m=read();m;--m) c[i][++ct[i]]=read();for(int i=1;i<=n;i++) if(!dfn[i]) dfs(i);for(int i=1;i<=n;i++){for(int j=1;j<=ct[i];j++)if(be[i]!=be[c[i][j]]) gt[be[i]][be[c[i][j]]]=true;}for(int i=1,res=0;i<=tot;res=0,i++){for(int j=1;j<=tot;j++)  if(i!=j&&gt[j][i]) res=1,link(j,i);if(!res) q[tl++]=i;}while(hd<tl){int x=q[hd++];for(int i=fs[x];i!=-1;i=nt[i]){G[to[i]]|=G[x]; if(!(--ind[to[i]])) q[tl++]=to[i];}}double ans=0.0;for(int i=1;i<=tot;i++) ans+=(sz[i]*1.0)/(G[i].count()*1.0);printf("Case #%d: %.5f\n",tt,ans);}return 0;
}