use proconio::input;

fn main() {
    input! {
        n: usize,
        ab: [(f64, f64); n],
        cd: [(f64, f64); n],
    }

    let ab_mean = [
        ab.iter().map(|x| x.0).fold(0., |acc, a| acc + a) / n as f64,
        ab.iter().map(|x| x.1).fold(0., |acc, a| acc + a) / n as f64,
    ];
    let cd_mean = [
        cd.iter().map(|x| x.0).fold(0., |acc, a| acc + a) / n as f64,
        cd.iter().map(|x| x.1).fold(0., |acc, a| acc + a) / n as f64,
    ];

    let ans = cd
        .iter()
        .map(|(c, d)| ((*c - cd_mean[0]).powi(2) + (*d - cd_mean[1]).powi(2)).sqrt())
        .fold(0., |acc, a| acc + a)
        / ab.iter()
            .map(|(a, b)| ((*a - ab_mean[0]).powi(2) + (*b - ab_mean[1]).powi(2)).sqrt())
            .fold(0., |acc, a| acc + a);
    println!("{}", ans);
}