#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define EPS (1e-7)
#define INF (1e9)
#define rep(i, n) for(int i = 0; i < (int)(n); i++)
#define all(x) x.begin(),x.end()
const double PI = acos(-1);
const ll MOD = 1000000007;
template<class T>
inline bool chmax(T &a, T b) {
    if(a < b) {
        a = b;
        return true;
    }
    return false;
}
 
template<class T>
inline bool chmin(T &a, T b) {
    if(a > b) {
        a = b;
        return true;
    }
    return false;
}
///////////////////////////////////////////////////////////////

int main() {
  ios::sync_with_stdio(false); cin.tie(nullptr); //入出力高速化
	int N; cin >> N;
	vector<int> A(N),B(N);
	rep(i,N) cin >> A[i];
	rep(i,N) cin >> B[i];

	vector<vector<bool>> win(N, vector<bool>(N,false));
	rep(i,N) {
		rep(j,N) {
			if (A[i] > B[j]) win[i][j] = true;
		}
	}

  vector<int> u(N),v(N);
	rep(i,N) u[i] = i;
  
	int q,r;
	q = r = 0;
	do {
		rep(i,N) v[i] = i;
    do {
      int p = 0;
      rep(i,N) {
				if (win[u[i]][v[i]]) p++;
			}
			if (2*p > N) q++;
			r++;
		} while (next_permutation(all(v)));
	} while (next_permutation(all(u)));
	
	cout << fixed << setprecision(10) << double(q) / double(r) << endl;
}