#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <bitset>
#include <queue>
typedef long long ll;
#define rep(i,n) for(int i = 0;i<n;++i)
#define repc(bit,k,n) for (int bit = (1<<k)-1;bit < (1<<n); bit = next_combination(bit))
#define repi(itr,vec) for(auto itr = vec.begin();itr!=vec.end();++itr)
using namespace std;
using Graph = vector<vector<int> >;

/* next combination
 * usage:repc(bit,k,n)
 * */
int next_combination(int sub) {
  int x = sub & -sub, y = sub + x;
  return (((sub & ~y) / x) >> 1) | y;
}

/* uniq
 * usage:uniq(vec)
 * */
void uniq(vector<int> &vec){
  sort(vec.begin(), vec.end());
  vec.erase(unique(vec.begin(), vec.end()), vec.end());
  return;
}

int main(){
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
  int n;cin>>n;
  vector<int> a(n),b(n);
  rep(i,n)cin>>a[i];
  rep(i,n)cin>>b[i];
  vector<int> v;
  rep(i,n)v.push_back(i);
  int ans = 0;
  int count = 0;
  do{
    int win = 0;
    rep(i,n){
      if(a[v[i]]>b[i])win++;
    }
    if(win*2>n)ans++;
    count++;
  }while(next_permutation(v.begin(),v.end()));
  cout << double(ans)/count << '\n';

        return 0;
}