#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int main () {
    int N;
    cin >> N;
    vector<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];
    }

    vector<int> va(N), vb(N);
    for (int i = 0; i < N; i++) {
        va[i] = i; vb[i] = i;
    }

    double game = 0;
    double wins = 0;

    do {
        do {
            int num = 0;
            for (int i = 0; i < N; i++) {
                if (A[va[i]] > B[vb[i]]) num ++;
            }
            game ++;
            if (num > N/2) wins ++; 
        } while(next_permutation(vb.begin(), vb.end()));
    } while(next_permutation(va.begin(), va.end()));

    long double ans = wins;

    ans /= game;

    cout << fixed << setprecision(10);
    cout << ans << endl;
    return 0;
}