#include<cstdio>
#include<bits/stdc++.h>

#define REP(i, n) for(int (i) = 0; (i) < (n); (i)++)
#define FOR_IN(i, a, b) for(int (i) = (a); (i) < (b); (i)++)
#define IN(x, a, b) ((x) >= (a) && (x) <= (b))

using namespace std;

/*
n <5
a0 a1 ...
b0 b1 ...
 */

int n;
int a[4];
int b[4];
int perm[4];

int fact(int n){
  if(n==0)
    return 1;
  else
    return n * fact(n-1);
}

int main(){
  cin >> n;
  REP(i,n){
    cin>>a[i];
  }
  REP(i,n){
    cin>>b[i];
  }

  REP(i,n)
    perm[i]=i;

  int win_num=0;
  do{
    int awin=0;
    int bwin=0;
    REP(i,n){
      //cerr << "a=" << a[i] << ", b=" << b[perm[i]] << "\n";
      if(a[i] > b[perm[i]]){
        //cerr << "a win!\n";
        awin++;        
      } else if(a[i] < b[perm[i]]){
        //cerr << "b win!\n";
        bwin++;
      }

    }
    if(awin>bwin)
      win_num++;
  }while(next_permutation(perm, perm+n));

  cout << ((double)win_num/(double)(fact(n))) << endl;
  
  return 0;
}