#include <bits/stdc++.h>

#define ALL(a) begin(a), end(a)
#define REP(i, n) for (int i = 0; i < static_cast<int>(n); ++i)

using ll = long long;
using ld = long double;
using byte = unsigned char;
using int128_t = __int128_t;
using uint128_t = __uint128_t;
using namespace std;

constexpr int IINF = 1e9 + 1;
constexpr ll LINF = 1e18 + 1;

// ================ Comment ================
// 
// =========================================

int main(int argc, char **argv)
{
    int N;
    cin >> N;
    vector<int> A(N), B(N);
    for (auto i = 0; N > i; i++) {
        cin >> A[i];
    }
    for (auto i = 0; N > i; i++) {
        cin >> B[i];
    }

    sort(ALL(A));
    sort(ALL(B));

    auto n_game_Awin = 0;
    auto n_games = 0;
    do {
        do {
            auto n_turn_Awin = 0;
            auto n_turn_Bwin = 0; 
            for (auto i = 0; N > i; i++) {
                if (A[i] > B[i]) {
                    n_turn_Awin++;
                }
                else {
                    n_turn_Bwin++;
                }
            }
            if (n_turn_Awin > n_turn_Bwin) {
                n_game_Awin++;
            }
            n_games++;
        } while (next_permutation(ALL(B)));
    } while (next_permutation(ALL(A)));

    cout << setprecision(15) << (double)n_game_Awin / n_games << endl;
    return EXIT_SUCCESS;
}