#include <bits/stdc++.h>
#define forn(i, n) for (int i = 0; i < (int)(n); ++i)
#define for1(i, n) for (int i = 1; i <= (int)(n); ++i)
#define fore(i, l, r) for (int i = (int)(l); i <= (int)(r); ++i)
#define ford(i, n) for (int i = (int)(n) - 1; i >= 0; --i)
#define all(v) (v).begin(), (v).end()
#define pb push_back
#define fi first
#define se second

using namespace std;

typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vi> vvi;
typedef vector<vll> vvl;
typedef pair<int, int> pint;
typedef vector<pint> vpint;

const int INF = 1e9;
const int MOD = 1e9+7;

vi A;
vi B;

int main(void)
{
  int N;
  cin >> N;
  A.resize(N);
  B.resize(N);
  forn (i, N) cin >> A[i];
  forn (i, N) cin >> B[i];

  sort(all(A));
  sort(all(B));

  ld ans;
  int cnt = 0, sum = 0;
  do {
    do {
      int scoreA = 0, scoreB = 0;
      forn (i, N) {
        if (A[i] > B[i]) ++scoreA;
        else ++scoreB;
      }
      if (scoreA > scoreB) ++cnt;
      ++sum;
    } while (next_permutation(all(B)));
  } while (next_permutation(all(A)));
  ans = (double)cnt / sum;
  cout << ans << endl;
}