#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
#include <string>
#include <set>
using namespace std;

int main() {
    int N; cin >> N;
    vector<int> 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.begin(), A.end());
    sort(B.begin(), B.end());

    // すべての順列をA,B両方で生成し，
    // 互いの先頭の要素から比較し合う（順列生成(N!)は入れ子
    int A_win = 0, btl_cnt = 0;
    int A_adv = 0, B_adv = 0;
    do {
        do {
            btl_cnt++;

            A_adv = 0, B_adv = 0;
            for (int i = 0; i < N; ++i) {
                if (A[i] > B[i]) A_adv++;
                else B_adv++;
            }
            if (A_adv > B_adv) A_win++;

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

    //cout << A_win << ' ' << btl_cnt << endl;
    cout << (double)A_win / (double)btl_cnt << endl;

}