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

int main()
{
    int N;
    cin >> N;

    int card1[N], card2[N];
    vector<string> pat;
    string tmp = "";

    for (int i = 0; i < N; i++) {
        cin >> card1[i];
        tmp += (i + '0');
    }
    for (int i = 0; i < N; i++) {
        cin >> card2[i];
    }

    do {
        pat.push_back(tmp);
    }while (next_permutation(tmp.begin(), tmp.end()));

    int count = 0, ans = 0;
    for (int i = 0; i < pat.size(); i++) {
        for (int j = 0; j < N; j++) {
            if (card1[pat[i][j] - '0'] > card2[j]) {
                count++;
            }
        }
        if (count > N / 2) {
            ans++;
        }
        count = 0;
    }

    cout << ans / (float)pat.size() << endl;
    return 0;
}