#include <bits/stdc++.h>
#include <iostream>
#include <vector>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
template <class T>
using V = vector<T>;
template <class T>
using VV = V<V<T>>;
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define fi first
#define se second
#define rep(i, n) rep2(i, 0, n)
#define rep2(i, m, n) for (int i = m; i < (n); i++)
#define per(i, b) per2(i, 0, b)
#define per2(i, a, b) for (int i = int(b) - 1; i >= int(a); i--)
#define ALL(c) (c).begin(), (c).end()
#define SZ(x) ((int)(x).size())
template <class T>ostream &operator<<(ostream &o,const vector<T>&v)
{o<<"{";for(int i=0;i<(int)v.size();i++)o<<(i>0?", ":"")<<v[i];o<<"}";return o;}

template <typename T> bool next_combination(const T first, const T last, int k) {
    const T subset = first + k;
    // empty container | k = 0 | k == n 
    if (first == last || first == subset || last == subset) {
        return false;
    }
    T src = subset;
    while (first != src) {
        src--;
        if (*src < *(last - 1)) {
            T dest = subset;
            while (*src >= *dest) {
                dest++;
            }
            iter_swap(src, dest);
            rotate(src + 1, dest + 1, last);
            rotate(subset, subset + (last - dest) - 1, last);
            return true;
        }
    }
    // restore
    rotate(first, subset, last);
    return false;
}
//""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
//""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
//""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
int main() {
   int N;
   double pt,win;
   pt=0,win=0;
   cin >> N;
   V<int> A(N);
   V<int> B(N);
   sort(ALL(A));
   sort(ALL(B));
   rep(i,N) {
      cin >> A[i];
   }
   rep(i,N) {
      cin >> B[i];
   }
   do{
      do{
         rep(i,N) {
            pt+=1.0;
            if (A[i]>B[i]){
               win+=1.0;
            }
         }
      
      }
      while (next_permutation(ALL(B)));
   }
   while (next_permutation(ALL(A)));
   cout <<  win/pt << endl;
}