//Normal

#define _GLIBCXX_DEBUG
#define ll long long
#include <bits/stdc++.h>
using namespace std;
using Graph = vector<vector<int>>;

void print(auto a){
  cout << a;
}

void prints(auto a){
  cout << a << " ";
}

void prints(){
  cout << " ";
}

void printl(auto a){
  cout << a << endl;
}

void printl(){
  cout << endl;
}

void fix(int n){
  cout << fixed << setprecision(n);
}

int 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];

  string S = "", T = "";
  for(int i = 0; i < N; i++){
    S += to_string(i);
    T += to_string(i);
  }

  int mat = 0;
  int win = 0;
  do{
    do{
      mat++;

      int po = 0;
      for(int i = 0; i < N; i++){
        int s = S[i]-'0';
        int t = T[i]-'0';

        if(A[s]-B[t] > 0) po++;
        else if(A[s]-B[t] < 0) po--;
      }

      if(po > 0) win++;
    }while(next_permutation(T.begin(), T.end()));
  }while(next_permutation(S.begin(), S.end()));

  double ans = (double)win/(double)mat;

  fix(10);
  printl(ans);

  return 0;
}