#include <bits/stdc++.h>
using namespace std;
int main() {
    int N;
    cin >> N;
    vector<int> A(N), B(N);
    for(int i = 0; i < N; i++) cin >> A.at(i);
    for(int i = 0; i < N; i++) cin >> B.at(i);
    
    vector<int> perm(N);
    for(int i = 0; i < N; i++) perm.at(i) = i;
    
    double bunshi = 0;
    double bumbo = 0;
    do {
        int A_win = 0;
        for(int i = 0; i < N; i++) {
            if(A.at(i) > B.at(perm.at(i))) A_win++;
        }
        if(A_win > N/2) bunshi++;
        bumbo++;
    } while (next_permutation(perm.begin(), perm.end()));
    
    double ans = bunshi / bumbo;
    cout << ans << endl;
}