#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;

int main(){
    int n;
    cin >> n;
    vector<int> a(n),b(n),ind(n);
    for(auto &x : a) cin >> x;
    for(auto &x : b) cin >> x;
    for(int i=0;i < n;i++) ind[i] = i;
    int all = 0,win = 0;
    
    do{
        int aa = 0;
        for(int i=0;i < n;i++){
            if(a[ind[i]] > b[i]) aa++;
            else aa--;
        }
        all++;
        if(aa > 0) win++;
    }while(next_permutation(ind.begin(),ind.end()));
    
    double ans = (double)win/(double)all;
    
    cout << ans << endl;
    return 0;
}