#include <bits/stdc++.h>

using namespace std;
#define rep(i,n) for (int i = 0; i < (int)(n); ++i)
#define rrep(i,n) for (int i = (int)(n-1); i >= 0; --i)
#define Rep(i,a,b) for (int i = a; i < b; ++i)
#define rRep(i,a,b) for (int i = a; i > b; --i)
#define fore(i,a) for(auto &i:a)
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define Bit(x,i) (((x)>>(i))&1)
using ll = long long;
using vi = vector<int>;
using vll = vector<long long>;
using vvi = vector<vi>;
using vvll = vector<vll>;
using vb = vector<bool>;
using vs = vector<string>;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
struct settings{settings(){ios_base::sync_with_stdio(0); cin.tie(0); cout<<fixed<<setprecision(15);};}settingss;
const double PI = acos(-1);
const int INF = 1001001001;
const ll LINF = 1001001001001001001LL;

int main() {
  int N; cin >> N;
  vi A, B;
  rep(i, N) {
    int a; cin >> a;
    A.push_back(a);
  }
  rep(i, N) {
    int b; cin >> b;
    B.push_back(b);
  }
  sort(all(A));
  sort(all(B));
  int cnt = 0;
  int A_win = 0;
  do {
    do {
      int tmp = 0;
      rep(i, N) {
        if(A[i] > B[i]) tmp++;
      }
      if(tmp > N/2) A_win++;
      cnt++;
    } while(next_permutation(all(A)));
  } while(next_permutation(all(B)));
  cout << double(A_win)/double(cnt) << endl;
}