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

double fact(int n) {
    switch (n) {
        case 3:
            return pow(6, 2);
        case 4:
            return pow(24, 2);
        default:
            return pow(n, 2);
    }
}

void solve() {
    int n;
    cin >> n;
    vector<int> a(n);
    vector<int> b(n);
    for (int i = 0; i < n; ++i) cin >> a[i];
    for (int i = 0; i < n; ++i) cin >> b[i];

    vector<int> pa(n);
    vector<int> pb(n);
    for (int j = 0; j < n; ++j) {
        pa[j] = j;
        pb[j] = j;
    }

    int a_win_c = 0;
    do {
        do {
            int a_win = 0;
            int b_win = 0;
            for (int i = 0; i < n; ++i) {
                int A = a[pa[i]];
                int B = b[pb[i]];
                if (B < A) ++a_win;
                else ++b_win;
            }
            if (b_win < a_win)  ++a_win_c;
        } while(next_permutation(pb.begin(), pb.end()));
    } while(next_permutation(pa.begin(), pa.end()));

    double all = fact(n);
    cout << (double)a_win_c / all << endl;
}

int main() {
    solve();
    return 0;
}