/* 
 *     Author:  srtry
 *     Created: 2025-05-10T01:29:57+09:00
 *     Coding:  utf-8-unix
 */

use proconio::input;
use std::io::{stdout,Write,BufWriter};

fn permutations(vec:&Vec<u8>) -> Option<Vec<Vec<u8>>> {
    if vec.len()==0 {
        return None;
    }
    if vec.len()==1 {
        return Some(vec![vec.clone()]);
    }

    let mut vec_ = vec.clone();
    let tmp:u8 = vec_.remove(0);
    let mut tmp2:Vec<u8>;
    let mut res = Vec::new();
    let pre = permutations(&vec_).unwrap();
    
    for elem in pre.iter() {
        for i in 0..=elem.len() {
            tmp2 = elem.clone();
            tmp2.insert(i,tmp);
            res.push(tmp2);
        }
    }
    return Some(res);
}

fn main() {
    input!{
        n:usize,
        a:[u8;n],
        b:[u8;n],
    }

    let out = stdout();
    let mut out = BufWriter::new(out.lock());
    
    // Aの並びは固定　Bの並び全パターン
    let b_ps = permutations(&b).unwrap();
    let mut win_games = 0;
    for b_p in b_ps.iter() {
        let mut win_cnt:u8 = 0;
        let mut lose_cnt:u8 = 0;
        for i in 0..n {
            if a[i] > b_p[i] {
                win_cnt += 1;
            } else if a[i] < b_p[i] {
                lose_cnt += 1;
            }
        }
        if win_cnt > lose_cnt {
            win_games += 1;
        }
    }

    write!(out, "{}", (win_games as f32)/(b_ps.len() as f32)).unwrap();
}