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

int N;
int A[4];
int B[4];

int permA[4], permB[4];
double vicA = 0, games = 0;

void permutation(int n) {
    for (int i = 0; i < n; i++) {
        permA[i] = A[i];
    }
    do {
        for (int i = 0; i < n; i++) {
            permB[i] = B[i];
        }
        do {
            double winA = 0, winB = 0;
            for (int j = 0; j < n; j++) {
                winA += (permA[j] > permB[j]);
                winB += (permA[j] < permB[j]);
            }
            vicA += (winA > winB);
            games++;
        } while (next_permutation(permB, permB + n));
    } while (next_permutation(permA, permA + n));
    return ;
}

int main() {
    cin >> N;
    double a[N], b[N];
    for (int i = 0; i < N; i++) cin >> a[i];
    for (int i = 0; i < N; i++) cin >> b[i];
    sort(a, a + N); sort(b, b + N);
    for (int i = 0; i < N; i++) A[i] = a[i], B[i] = b[i];
    permutation(N);
    double pA = vicA / games;
    cout << pA << endl;
    return 0;
}