Counting Parallelogram

#include<bits/stdc++.h>
#define endl '\n'
using namespace std;
void solve();
int x,t = 1;
int main() {

	cin >> t; x=t;
	while (t--) {
		solve();
	}
	return 0;
}

void solve() {
	int i,j;
	int n; cin >> n;
	vector<pair <long long , long long >> p ;
	map < pair <long double , long double >,long long> mp;
	set<pair<long double,long double>> st;
	for(i=0;i<n;i++){
		int a,b;
		cin>>a>>b;
		p.push_back({a,b});
	}
	for(i=0;i<n;i++){
		for(j=i+1;j<n;j++){
			pair<long double, long double> y={(p[i].first+p[j].first)/2.0,(p[i].second+p[j].second)/2.0  };
			mp[y]++;
			st.insert(y);

		}
	}
	long long sum=0;

	for(auto it: st){
		sum += (mp[it] * (mp[it]-1))/2;

	}
	cout<<"Case "<<x-t<<": "<<sum<<endl;
}