#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define sz(x) int(x.size())
using namespace std;

typedef long long ll;
typedef pair<ll, ll> P;
// const ll INF = 1LL << 60;
const int INF = 1e8;

const int mod = 1000000007;

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

    rep(i, N) cin >> A[i];
    rep(i, N) cin >> B[i];
    sort(A.begin(), A.end());
    sort(B.begin(), B.end());

    int games = 0;
    int game_win_a = 0;
    do {
        do {
            int win_a = 0, win_b = 0, draw = 0;;
            rep(i, N) {
                if (A[i] > B[i]) {
                    win_a++;
                } else if (A[i] < B[i]) {
                    win_b++;
                } else {
                    draw++;
                }
            }
            if (win_a > win_b) game_win_a++;

            games++;
        } while (next_permutation(B.begin(), B.end()));
    } while (next_permutation(A.begin(), A.end()));

    double ans = (double)game_win_a / games;
    printf("%.5f\n", ans);
}