#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
using namespace std;
using ll = long long;
template<class T> inline bool chmax(T &a, T b) { if (a<b) {a=b; return 1;} return 0;}
template<class T> inline bool chmin(T &a, T b) { if (b<a) {a=b; return 1;} return 0;}

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

    int tot = 0;
    int win = 0;
    iota(permA.begin(), permA.end(), 0);
    do {
        iota(permB.begin(), permB.end(), 0);
        do {
            tot++;
            int cur_win = 0;
            rep(i, n) {
                int cur_a = a[permA[i]];
                int cur_b = b[permB[i]];
                if (cur_a > cur_b) cur_win++;
            }
            int cur_lose = n - cur_win;
            if (cur_win > cur_lose) win++;

        } while (next_permutation(permB.begin(), permB.end()));
    } while (next_permutation(permA.begin(), permA.end()));

    double ans = (double)win / tot;
    cout << ans << endl;
}