#include <iostream>
#include <bits/stdc++.h>
using namespace std;
#define mp make_pair
#define REP(A,B) for(int (A)=0;(A)<(B);(A)++)

#define pb push_back
int matched[3*1100*4];

int main() {
	int n;
	scanf("%d", &n);
	vector< pair<int, int> > hs;
	map<pair<int,int>,int > S;
	n = 4*n;
	REP(i, n) {
		int x,y;
		scanf("%d%d", &x, &y);
		hs.pb(mp(x, y));
		S[mp(x, y)] = i;
	}
	sort(hs.begin(), hs.end());
	long double ans = 0;
	REP(i, n) {
		if(matched[i])
			continue;
		for(int j = i+1; j < n; j++) {
			if(matched[j])
				continue;
			int dx = (hs[j].first-hs[i].first);
			int dy = (hs[j].second-hs[i].second);
			if(dx % 2 != dy % 2)
				continue;

			int xa = hs[i].first+(dx+dy)/2;
			int xb = hs[i].first+(dx-dy)/2;
			int ya = hs[i].second+(-dx+dy)/2;
			int yb = hs[i].second+(dx+dy)/2;
			if(!S.count(mp(xa,ya)))
				continue;
			if(!S.count(mp(xb,yb)))
				continue;
			if(matched[S[mp(xa,ya)]])
				continue;
			if(matched[S[mp(xb,yb)]])
				continue;

			matched[i] = matched[j] = matched[S[mp(xa,ya)]] = matched[S[mp(xb,yb)]] = 1;
			long double curr = (dx*(long double)dx+dy*(long double)dy)/2.0L;
			ans += curr;
		}
	}
	printf("%.8Lf", ans);
	
	return 0;

}