#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
using namespace std;

double solve(const vector<int>& a, const vector<int>& b, bitset<4> bs, int diff)
{
    int n = a.size();
    int j = bs.count();
    if(j == n){
        if(diff > 0)
            return 1.0;
        else
            return 0.0;
    }

    double ret = 0.0;
    for(int i=0; i<n; ++i){
        if(!bs[i]){
            bs[i] = true;
            if(a[i] > b[j])
                ret += solve(a, b, bs, diff + 1);
            else if(a[i] < b[j])
                ret += solve(a, b, bs, diff - 1);
            else
                ret += solve(a, b, bs, diff);
            bs[i] = false;
        }
    }
    ret /= n - j;
    return ret;
}

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];

    printf("%.10f\n", solve(a, b, 0, 0));
    return 0;
}