#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];
#define ll long long

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));
	}
	sort(hs.begin(), hs.end());
	REP(i, n) {
		S[mp(hs[i].first, hs[i].second)] = i;
	}
	long double ans = 0;
	REP(i, n) {
		if(matched[i])
			continue;
		int closest = -1;
		long long closestdist = 1LL<<62;
		int o1 = -1;
		int o2 = -1;
		for(int j = i+1; j < n; j++) {
			if(matched[j])
				continue;
			ll dx = (hs[j].first-hs[i].first);
			ll dy = (hs[j].second-hs[i].second);
			if(dx % 2 != dy % 2)
				continue;

			int xa = hs[i].first+(dx+dy)/2;
			int ya = hs[i].second+(-dx+dy)/2;

			int xb = hs[i].first+(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;
			int k1 = S[mp(xa,ya)];
			int k2 = S[mp(xb,yb)];
			/*printf("[%d %d] [%d %d]: [%d %d] [%d %d], k1=%d, k2=%d\n", 
				hs[i].first, hs[i].second, hs[j].first, hs[j].second, xa, ya, xb, yb
			k1, k2);*/
			if(matched[k1])
				continue;
			if(matched[k2])
				continue;

			long long cdist = dx*dx+dy*dy;
			if(cdist < closestdist) {
				closestdist = cdist;
				closest = j;
				o1 = k1;
				o2 = k2;
			}
		}
		//printf("%d %d %d %d\n", i, closest, o1, o2);
		matched[i] = matched[closest] = matched[o1] = matched[o2] = 1;
		//printf("%lld\n", closestdist);
		ans += closestdist/2.0L;
	}
	printf("%.8lf\n", (double)ans);
	
	return 0;

}