#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define llong long long

int main() {
    int n;
    cin >> n;
    vector<int> a(n), b(n), idx(n);
    rep(i, n) cin >> a[i];
    rep(i, n) cin >> b[i];
    rep(i, n) idx[i] = i;

    vector<vector<int>> perm;
    int wins = 0;
    int total = 0;
    do {
        perm.push_back(idx);
    } while(next_permutation(idx.begin(), idx.end()));
    for(vector<int> a1: perm) {
        for(vector<int> b1: perm) {
            int win = 0;
            rep(i, n) {
                if(a[a1[i]] > b[b1[i]]) win++;
            }
            if(win*2 > n) wins++;
            total++;
        }
    }

    printf("%5f\n", (double)wins / (double)total);
}