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

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int INF = 1e9;

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];
    }

    vector<int> p1(n), p2(n);
    for (int i = 0; i < n; ++i) {
        p1[i] = i;
        p2[i] = i;
    }

    int res = 0;
    int num = 0;
    do{
        do{
            int tmp = 0;
            for (int i = 0; i < n; ++i) {
                if(a[p1[i]] > b[p2[i]]) tmp++;
            }
            if(tmp > n - tmp) res++;
            num++;
        }while(next_permutation(p2.begin(), p2.end()));
        for (int i = 0; i < n; ++i) {
            p2[i] = i;
        }
    }while(next_permutation(p1.begin(), p1.end()));

    cout << (double)res / (double)num << endl;
}