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

signed 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];sort(b.begin(),b.end());

  long double ans=0,cnt=0;
  do{
    cnt++;
    int win=0,lose=0;
    for(int i=0;i<n;i++){
      if(a[i]>b[i])win++;
      else lose++;
    }
    if(win>lose)ans++;
  }while(next_permutation(b.begin(),b.end()));
  cout<<ans/cnt<<endl;
}