#include <iostream>
#include <vector>
using namespace std;

int N;
vector<int> A, B;
vector<int> perm_A;
vector<int> perm_B;
vector<bool> used_A;
vector<bool> used_B;

int num_A, num_B;

void dfs(int time) {
    if (time == N) {
        // cout << "time == N" << endl;
        int a = 0, b = 0;
        for (int i = 0; i < N; i++) {
            if (A[perm_A[i]] > B[perm_B[i]]) {
                // num_A++;
                a++;
            } else {
                // num_B++;
                b++;
            }
        }
        if (a > b) num_A++;
        else num_B++;
    }

    for (int i = 0; i < N; i++) {
        if (!used_A[i]) {
            perm_A[time] = i;
            used_A[i] = true;

            for (int j = 0; j < N; j++) {
                if (!used_B[j]) {
                    perm_B[time] = j;
                    used_B[j] = true;
                    dfs(time + 1);
                    used_B[j] = false;
                }
            }

            used_A[i] = false;
        }
    }

    return;
}

int main() {
    cin >> N;
    // vector<int> A(3), B(3);
    A.resize(N);
    B.resize(N);

    for (int i = 0; i < N; i++) cin >> A[i];
    for (int i = 0; i < N; i++) cin >> B[i];

    used_A.resize(N);
    used_B.resize(N);
    // memset(used_A)
    used_A.assign(N, false);
    used_B.assign(N, false);

    perm_A.resize(N);
    perm_B.resize(N);

    // cout << "here?" << endl;

    num_A = 0;
    num_B = 0;

    dfs(0);

    // cout << num_A << " " << num_B << endl;
    cout << (double)num_A / (double)(num_A + num_B) << endl;
}