#include<iostream>
#include<algorithm>
using namespace std;
int main() {
    int n; cin >> n;
    int a[n], b[n];
    for (int i = 0; i < n; ++i) {
        cin >> a[i];
    }
    for (int i = 0; i < n; ++i) {
        cin >> b[i];
    }
    int ans = 0;
    int cnt = 0;
    sort(a, a + n);
    do {
        for (int i = 0; i < n; ++i) {
            if (a[i] > b[i]) {
                cnt++;
            }
        }
        if (cnt > n / 2) {
            ans++;
        }
        cnt = 0;
    } while (next_permutation(a, a + n));
    int sum = 1;
    for (int i = n; i >= 2; --i) {
        sum *= i;
    }
    //cout << ans << " " << sum << endl;
    cout << (double)ans / sum << endl;
}