#include <bits/stdc++.h>
using namespace std;

#define rep(i,a,b) for(ll i=a;i<b;i++)
#define rrep(i,b,a) for(ll i=b;i>=a;i--)
#define fori(i,a) for(auto i : a )
#define all(a) begin(a), end(a)
#define mset(a,b) memset(a,b,sizeof(a))
#define mcopy(a,b) memcopy(a,b,sizeof(a))
#define pb push_back
#define f first
#define s second
#define ll long long
string getString(char x) {
    string s(1, x);
    return s;
}
void solve1(){
  vector<pair<ll,string>> v(10001);
  rep(i,1,10001){
    cin>>v[i].f>>v[i].s;
  }
  sort(all(v));
  vector< set<string> > v1(100);
  rep(i,1,10001){
    v1[v[i].f].insert(v[i].s);
  }
  string s="";
  rep(i,1,11){
    if(i==1)s+=*v1[i].begin();
    else{
      for(auto j:v1[i]){
        if(v1[i-1].find(j)==v1[i-1].end()){
          if(i!=10) s+=j;
          else{
            s=getString(j[1])+s;
          }
          break;
        }
      }
    }
  }
  cout<<s<<endl;
}
void solve3(vector<pair<ll,string>> v){
  map<char,int> m1;
  set<char> s1;
  for(auto i:v){
    for(auto j:i.s){
      s1.insert(j);

    }
  }
  set<char> s2=s1;
  for(auto i:v){
    s2.erase(i.s[0]);
    m1[i.s[0]]++;
  }
  string g="";
  char fi;
  int mx=0;
  for(auto i:s2){
    // if(mx>m1[i]){
    //   mx=m1[i];
      fi=i;
    // }
  }
  g+=getString(fi);
  s1.erase(fi);
  s2.erase(fi);
  m1.erase(fi);
  vector<pair<int,char>> v1;
  for(auto i:s2) m1[i]=0;
  for(auto i:m1){
    v1.pb({i.s,i.f});
  }
  // sort(v1.begin(),v1.end());
  sort(v1.begin(),v1.end(),greater<pair<int,char>>());
  for(auto i:v1) g+=getString(i.s);
  cout<<g<<endl;
}
void solve2(){
  vector<pair<ll,string>> v(10001);
  ll flag=0;
  rep(i,1,10001){
    cin>>v[i].f>>v[i].s;
    if(v[i].f!=-1) flag=1;
  }
  auto comp=[]( const pair<ll,string> & x , const pair<ll,string> &y ){return x.s.length()<y.s.length();};
  sort(all(v),comp);
  // solve3(v);
  if(flag==0)solve3(v);
  else{
    set<char> s1;
    for(auto i:v){
      for(auto j:i.s){
        s1.insert(j);
      }
    }
    vector<pair<ll,string>> v1;
    map<ll,set<char>> m1;
    rep(i,1,10001){
      if(v[i].f!=-1){
        v1.pb({v[i].f,v[i].s});
      }
    }
    rep(i,0,v1.size()){
      if(to_string(v1[i].f).length()==v1[i].s.length()) m1[to_string(v1[i].f)[0]-'0'].insert(v1[i].s[0]);
    }
    string g="";
    g+=getString(*m1[1].begin());
    // cout<<g<<endl;
    rep(i,2,10){
      for(auto j:m1[i]){
        if(m1[i-1].find(j)==m1[i-1].end()){
          g+= getString(j);
        }
      }
    }
    // cout<<g<<endl;
    for(auto i:s1){
      if(g.find(i)==string::npos){
        g=getString(i)+g;
        break;
      }
    }
    cout<<g<<endl;
  }
}
void solve(){
  ll u;
  cin>>u;
  if(u==2) solve1();
  else solve2();
}
int main(){
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);

  // freopen("input.txt", "r", stdin);
  // freopen("output.txt", "w", stdout);

  ll t,k=1;
  cin>>t;
  while(t--){
    cout<<"Case #"<<k++<<": ";
    solve();
  }
}