vector +( pair pair and pair)

// In the name of Allah.
// We're nothing and you're everything.
// Ya Ali!
/*
                  ,     \    /      ,
                 / \    )\__/(     / \
                /   \  (_\  /_)   /   \
           ____/_____\__\@  @/___/_____\____
          |             |\../|              |
          |              \VV/               |
          |        ------___-------         |
          |__________Chuta Dragon___________|
           |    /\ /      \\       \ /\    |
           |  /   V        ))       V   \  |
           |/     `       //        '     \|
           `              V                '
        */

#include<bits/stdc++.h>
using namespace std;
typedef  long long ll;
typedef pair<ll,ll>pll;
#define fastread() (ios_base:: sync_with_stdio(false),cin.tie(NULL))
#define fi first
#define se second
#define pb push_back
ll const MOD=1000000007;
///-------------------------------------------------------------------------------------------------///
///                KARMA IS LIKE 69,,, YOU GET WHAT YOU GIVE                                        ///
///-------------------------------------------------------------------------------------------------///
void input(ll ara[],ll n)
{
    for(ll i=0; i<n; i++)
        cin>>ara[i];
}

void output(ll ara[],ll n)
{
    for(ll i=0; i<n; i++)
        cout<<ara[i]<<" ";
}

ll mx1(ll ara[],ll n)
{
    ll mx=-1;
    for(ll i=0; i<n; i++)
        if(ara[i]>mx)
            mx=ara[i];
    return mx;
}
ll mn1(ll ara[],ll n)
{
    ll mn=1e18;
    for(ll i=1; i<=n; i++)
        if(ara[i]<mn)
            mn=ara[i];
    return mn;
}

#define eb emplace_back


int main()
{
     fastread();

     ll t;
ll kase=1;

    cin>>t;

    while(t--)
    {
      ll n;


      cin>>n;



    vector<pair<ll,pair<ll,ll>>>v;

     for(ll i=0;i<n;i++)
     {


         ll a,b;

         cin>>a>>b;


       v.push_back({a,{b,i}});


     }


     sort(v.begin(),v.end());



   for(ll i=0;i<n;i++)
     {


         cout<<v[i].first<<" ";


        cout<<v[i].second.first<<" ";
        cout<<v[i].second.second<<endl;


     }

     ll j=0,c=0;
     bool f=true;
     char ara[n+1];

     for(ll i=0;i<n;i++)
     {
         if(v[i].first>=j )
         {
             ara[v[i].second.second]='J';
             j=v[i].second.first;

         }else if(v[i].first>=c )
         {
             ara[v[i].second.second]='C';
            c=v[i].second.first;
         }else
         {
             f=false ;

             break;
         }

     }

     cout<<"Case #<<"<<kase++<<": ";
    if(f)
    {
        for(ll i=0;i<n;i++)
        {
            cout<<ara[i];
        }
        cout<<endl;

    }
    else cout<<"IMPOSSIBLE"<<endl;








     }








     }