#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0; i<(int)n; i++)
#define repi(i,m,n) for(int i=(int)m; i<=(int)n; i++)
#define rrep(i,n) for(int i=(int)n-1; i>=0; i--)
#define rrepi(i,m,n) for(int i=(int)n; i>=(int)m; i--)
#define all(x) x.begin(),x.end()
template <typename T> inline bool chmin(T& a, const T& b) { return a > b ? a = b, true : false; };
template <typename T> inline bool chmax(T& a, const T& b) { return a < b ? a = b, true : false; };
template <typename T> void uniq(std::vector<T> &v){
    std::sort(v.begin(),v.end());
    v.erase(unique(v.begin(),v.end()),v.end());
}
using ll = long long;

int main(){
    int n; cin >> n;
    vector<double> x(n),y(n);
    double sx = 0,sy = 0,tx = 0,ty = 0,sd = 0,td = 0;
    rep(i,n){
        cin >> x[i] >> y[i];
        sx += x[i]; sy += y[i];
    }
    sx /= n; sy /= n;
    rep(i,n) sd += hypot(x[i]-sx,y[i]-sy);

    rep(i,n){
        cin >> x[i] >> y[i];
        tx += x[i]; ty += y[i];
    }
    tx /= n; ty /= n;
    rep(i,n) td += hypot(x[i]-tx,y[i]-ty);

    cout << fixed << setprecision(15) << td/sd << endl;
    
    return 0;
}