#include<bits/stdc++.h>
#define pb push_back
#define fi first
#define se second
#define bit(s,x) (((s)>>(x))&1)
#define pnp(s) __builtin_popcountll(s)
#define rep(i,a,b) for(int i=(a);i<=(b);++i)
#define per(i,a,b) for(int i=(a);i>=(b);--i)
using namespace std;
typedef long long ll; 
typedef unsigned long long ull;
typedef pair<int,int> pii;
inline ll read(){
	ll x=0,f=1,c=getchar();
	while(c<'0'||c>'9')f=(c=='-'?-1:1),c=getchar();
	while(c>='0'&&c<='9')x=(x<<1)+(x<<3)+(c^48),c=getchar();
	return x*f;
}
const int N=3003;
int n;
struct P{ int x,y,id; };
struct tr{ P a[3];};
inline bool operator <(P A,P B){return A.x==B.x?A.y<B.y:A.x<B.x;}
vector<P>a;
vector<tr>b;
inline ll cr(P A,P B,P C){return 1ll*(B.x-A.x)*(C.y-A.y)-1ll*(B.y-A.y)*(C.x-A.x);}
inline ll dist(P A,P B){return 1ll*(B.x-A.x)*(B.x-A.x)+1ll*(B.y-A.y)*(B.y-A.y);}
int testid;
inline void get(vector<P>&A,vector<P>&B){
	P x=A[0],y=A[1];
	auto w1=min_element(B.begin(),B.end(),[&](P A,P B){return cr(y,A,B)?cr(y,A,B)>0:dist(y,A)<dist(y,B);});
	auto w2=min_element(B.begin(),B.end(),[&](P A,P B){return cr(y,A,B)?cr(y,A,B)<0:dist(y,A)<dist(y,B);});
	auto w=cr(x,y,*w1)<0?w1:w2;
	b.pb({x,y,*w});
	A.erase(A.begin()),A.erase(A.begin()),B.erase(w);
}
inline bool cross(P a1,P b1,P a2,P b2){
	if(!cr(a1,b1,a2)||!cr(a1,b1,b2)||!cr(a2,b2,a1)||!cr(a2,b2,b1)){
		return !cr(a1,b1,a2)&&!cr(a1,b1,b2)&&min(a2,b2)<max(a1,b1)&&min(a1,b1)<max(a2,b2);
	}
	return ((cr(a1,b1,a2)>0)^(cr(a1,b1,b2)>0))&&((cr(a2,b2,a1)>0)^(cr(a2,b2,b1)>0));
}
inline bool ck(tr A,tr B){
	rep(i,0,2)rep(j,i+1,2)rep(k,0,2)rep(l,k+1,2){
		bool fl=cross(A.a[i],A.a[j],B.a[k],B.a[l]);
		if(fl)return 1;
	}
	return 0;
}
inline void print(){
	printf("Case #%d: %ld\n",testid,b.size());
	for(tr A:b)printf("%d %d %d\n",A.a[0].id,A.a[1].id,A.a[2].id);
	//rep(i,0,(int)b.size()-1)rep(j,0,i-1) assert(!ck(b[i],b[j]));
	a.clear(),b.clear();
}
inline void solve(){
	++testid;
	n=read();
	rep(i,1,n){
		int x=read(),y=read();
		a.pb({x,y,i});
	}
	sort(a.begin(),a.end());
	while(a.size()>=3){
		P x=a[0],y=a[1];
		auto w1=min_element(a.begin()+2,a.end(),[&](P A,P B){return cr(y,A,B)?cr(y,A,B)>0:dist(y,A)<dist(y,B);});
		auto w2=min_element(a.begin()+2,a.end(),[&](P A,P B){return cr(y,A,B)?cr(y,A,B)<0:dist(y,A)<dist(y,B);});
		auto w=a.end();
		if(cr(x,y,*w1)<0)w=w1;
		else if(cr(x,y,*w2)>0)w=w2;
		else break;
		b.pb({x,y,*w});
		a.erase(w);a.erase(a.begin());a.erase(a.begin());
	}
	if(a.size()<3){print();return;}
	P x=a[0],y=a[1];
	vector<P>A=a,B,C;
	while(A.size()%3)A.pop_back();
	while(b.size()&&A.size()>2*(B.size()+C.size())){
		tr res=b.back();b.pop_back();
		rep(d,0,2){
			P p=res.a[d];
			if(cr(x,y,p)==0)A.pb(p);
			else if(cr(x,y,p)>0)B.pb(p);
			else C.pb(p);
		}
	}
	while(A.size()>2*(B.size()+C.size()))A.pop_back();
	sort(A.begin(),A.end());
	if(B.size()>C.size())swap(B,C);
	if(A.size()==2*(B.size()+C.size())){
		while(B.size())get(A,B);
		while(C.size())get(A,C);
	}
	else{
		while(A.size()>3&&B.size())get(A,B);
		while(A.size()>3&&C.size())get(A,C);
		for(P x:B)A.pb(x);
		for(P x:C)A.pb(x);
		assert(A.size()==6);
		rep(i,0,5)rep(j,i+1,5)rep(k,j+1,5){
			bool vis[6]={0};vis[i]=vis[j]=vis[k]=1;
			int x=0;while(vis[x])++x;
			int y=x+1;while(vis[y])++y;
			int z=y+1;while(vis[z])++z;
			if(cr(A[i],A[j],A[k])&&cr(A[x],A[y],A[z])&&!ck({A[i],A[j],A[k]},{A[x],A[y],A[z]})){
				b.pb({A[i],A[j],A[k]});
				b.pb({A[x],A[y],A[z]});
				print();return ;
			}
		}
	}
	print();
}
int main() {
    //freopen("data.in", "r", stdin);
    //freopen("myans.out","w",stdout);
	int T=read();while(T--)solve();
    return 0;
}