#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include<iostream>
#include<cstdint>
#include<cstddef>
#include<vector>
#include<algorithm>
#include<iomanip>
//#include<atcoder/all>
//using namespace atcoder;
using namespace std;
using i32 = int_fast32_t;
using i64 = int_fast64_t;
using usize = uint_fast64_t;
#define rep(i, n) for (i64 i = 0; i < (i64)(n); ++i)
#define all(a) (a).begin(),(a).end()
#define rall(a) (a).rbegin(),(a).rend()
using P = pair<i64,i64>;

int main(){
    ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    i64 n;
    cin >> n;
    i64 cnt = 0;
    vector<i64> a(n),b(n);
    rep(i,n)cin >> a[i];
    rep(i,n)cin >> b[i];
    sort(all(a));
    sort(all(b));
    do{
        do{
            i64 wins = 0;
            rep(i,n) {
                if (a[i] > b[i])wins++;
            }
                if(wins > n / 2)cnt++;
        }while (next_permutation(all(a)));
    }while(next_permutation(all(b)));
    i64 sum = 1;
    rep(i,n){
     sum *= (i + 1);
    }
    sum *= sum;
cout << setprecision(10) << (long double)(cnt) / sum << endl;
}