#include <iostream>
#include <iomanip>
#include <cmath>
#include <string>
#include <vector>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <queue>
#include <numeric>
#include <random>
#include <algorithm>
#include <functional>
#include <cassert>

using namespace std;
typedef long long ll;

template<class T> inline bool chmin(T& a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template<class T> inline bool chmax(T& a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

const int INF = (1 << 30) - 1;
const ll INFLL= (1LL << 61) - 1;
const int MOD = 1000000007;
#define ALL(a) (a).begin(),(a).end()
#define rALL(a) (a).rbegin(),(a).rend()
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)

int main(){
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  int N;
  cin>>N;
  vector<int>A(N),B(N);
  REP(i,N)cin>>A[i];
  REP(i,N)cin>>B[i];
  sort(ALL(A));
  sort(ALL(B));
  int win=0,lose=0;
  do {
    do{
      int win1=0,lose1=0;
      REP(i,N){
        if(A[i]<B[i]){
          lose1++;
        }else{
          win1++;
        }
      }
      if(win1>lose1)win++;
      else lose++;
    } while (next_permutation(ALL(B)));
  } while (next_permutation(ALL(A)));
  cout<<double(win)/(win+lose)<<endl;
}