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

struct Precision{
  Precision(){
    cout<<fixed<<setprecision(12);
  }
}precision_beet;

//INSERT ABOVE HERE
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];

  double ans=0,cnt=0;
  sort(a.begin(),a.end());
  do{
    sort(b.begin(),b.end());
    do{
      Int x=0,y=0;
      for(Int i=0;i<n;i++) if(a[i]>b[i]) x++;else y++;
      if(x>y) ans+=1;
      cnt+=1;
    }while(next_permutation(b.begin(),b.end()));
  }while(next_permutation(a.begin(),a.end()));
  
  
  cout<<ans/cnt<<endl;
  return 0;
}