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

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

    vector<int> a(N), b(N), perm(N);
    for (int i = 0; i < N; i++) cin >> a[i];
    for (int i = 0; i < N; i++) cin >> b[i];
    for (int i = 0; i < N; i++) perm[i] = i;

    int ptn =0, awin = 0;
    int cnt;
    do {
        ptn++;
        cnt = 0;
        for (int i = 0; i < N; i++) {
            if (a[perm[i]] > b[i]) cnt++;
        }
        if (cnt > N / 2) awin++;
    } while (next_permutation(perm.begin(), perm.end()));
    double ans = (double) awin / ptn;
    printf("%.2f\n", ans);

}