#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); i++)
using namespace std;
using ll = long long;
using pii = pair<int, int>;

int main() {
  int n;
  cin >> n;
  vector<int> a(n), b(n);
  rep(i, n) cin >> a[i];
  rep(i, n) cin >> b[i];

  int tot = 0, win = 0;
  vector<int> pa(n), pb(n);
  rep(i, n) pa[i] = pb[i] = i;
  do {
    do {
      int a_win = 0, b_win = 0;
      rep(i, n) {
        if (a[pa[i]] > b[pb[i]]) a_win++;
        else b_win++;
      }
      if (a_win > b_win) win++;
      tot++;
    } while (next_permutation(pb.begin(), pb.end()));
  } while (next_permutation(pa.begin(), pa.end()));

  double ans = (double)win / tot;
  printf("%.15f\n", ans);
  return 0;
}