#include <bits/stdc++.h>
#define debug(x) cerr << #x << ": " << x << '\n';
using namespace std;
using ll = long long;
using Point = pair<int, int>;
const int INF = (int)1e9;

#ifndef FACT
#define FACT
// return n! mod p
int fact(int n, int p = __INT32_MAX__){
	static vector<int> memo_in_fact(1, 1);
	if ((int) memo_in_fact.size() <= n) {
		int l = memo_in_fact.size();
		memo_in_fact.resize(n+1);
		for(int i = l; i <= n; i++) memo_in_fact[i] = ((ll) memo_in_fact[i-1] * i) % p;
	}
	return memo_in_fact[n];
}
#endif

int N;
int A[4], B[4];

int main(void){
    cin >> N;
    for(int i = 0; i < N; i++) cin >> A[i];
    for(int i = 0; i < N; i++) cin >> B[i];

    sort(A, A+N); sort(B, B+N);
    int res = 0;

    do{
        do{
            int win_a = 0, win_b = 0;
            for(int i = 0; i < N; i++){
                if(A[i] > B[i]) win_a++;
                if(A[i] < B[i]) win_b++;
            }
            if(win_a > win_b) res++;
        }while(next_permutation(B, B+N));
    }while(next_permutation(A, A+N));

    cout << (double)res / fact(N) / fact(N) << '\n';

    return 0;
}