#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main(){
  int N,A,B;
  cin>>N;
  vector<int> va;
  for(int i=0; i<N; ++i){
    cin>>A;
    va.push_back(A);
  }
  vector<int> vb;
  for(int i=0; i<N; ++i){
    cin>>B;
    vb.push_back(B);
  }
  vector<int> vi1;
  for(int i=0; i<N; ++i){
    vi1.push_back(i);
  }
  vector<int> vi2;
  for(int i=0; i<N; ++i){
    vi2.push_back(i);
  }
  double wa=0,wb=0,dr=0;
  do{
    do{
      double wa2=0,wb2=0,dr2=0;
      for(int i=0; i<N; ++i){
        int ind1=vi1[i];
        int ind2=vi2[i];
        if(va[ind1]>vb[ind2]){
          wa2+=1;
        } else if(va[ind1]<vb[ind2]){
          wb2+=1;
        } else if(va[ind1]==vb[ind2]){
          dr2+=1;
        }
      }
      if(wa2>wb2){
        wa+=1;
      } else if(wa2<wb2){
        wb+=1;
      } else if(wa2==wb2){
        dr+=1;
      }
    } while(next_permutation(vi2.begin(),vi2.end()));
  } while(next_permutation(vi1.begin(),vi1.end()));
  double ans=wa/(wa+wb+dr);
  cout<<ans<<endl;
  return 0;
}