#include<bits/stdc++.h>
using namespace std;
int flag;
struct pt {
    int x,y,z;
};
bool cmp(pt a, pt b) {
    return a.x < b.x || (a.x == b.x && a.y < b.y);
}
int area(pt a, pt b, pt c) {
    return a.x*(b.y-c.y)+b.x*(c.y-a.y)+c.x*(a.y-b.y);
}
vector<int> convex_hull(vector<pt>& a) {
    sort(a.begin(), a.end(), &cmp);
    pt p1 = a[0], p2 = a.back();
    vector<int> up, down,p;
    up.push_back(p1.z);
    for (int i = 1; i < (int)a.size()-1; i++) {
        if (area(p1, a[i], p2)<0) {
            flag=2;
        }
        else if (area(p1, a[i], p2)>0) {
            down.push_back(a[i].z);
            flag=1;
        }
    }
    for (int i = 1; i < (a.size()-1); i++) {
        if (area(p1, a[i], p2)==0) {
            if(flag==2)down.push_back(a[i].z);
            else
            up.push_back(a[i].z);
        }
        else if (area(p1, a[i], p2)>0) {
            down.push_back(a[i].z);
        }
        else
        {
             up.push_back(a[i].z);
        }
    }
    down.push_back(p2.z);
    for (int i = 0; i < (int)a.size()-1; i++) {
            if(a[i].x==a[i+1].x&&a[i].y==a[i+1].y)flag=0;
    }
    a.clear();
    for (int i = down.size() -1; i >=0; i--)
        up.push_back(down[i]);
    return up;
}
int main()
{
    int i,j,k,t,n,x,y,z;
    cin>>t;
    z=t;
    while(t--)
    {
        cin>>n;
        flag=0;
        vector<pt>v;
        for(i=0;i<n;i++)
        {
            cin>>x>>y;
            v.push_back({x,y,i});
        }
        vector<int>p=convex_hull(v);
        cout<<"Case "<<z-t<<":\n";
        if(flag==0)
        { cout<<"Impossible"<<endl;
            continue;
        }
        for(i=0;i<n;i++)
            cout<<p[i]<<" ";
        cout<<endl;
    }
}