#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i < n; i++)
#define rep2(i, x, n) for(int i = x; i <= n; i++)
#define rep3(i, x, n) for(int i = x; i >= n; i--)
#define elif else if
#define sp(x) fixed << setprecision(x)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define sz(x) (int)x.size()
using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
const ll MOD = 1e9+7;
//const ll MOD = 998244353;
const int inf = (1<<30)-1;
const ll INF = (1LL<<60)-1;
const ld EPS = 1e-10;
template<typename T> bool chmax(T &x, const T &y) {return (x < y)? (x = y, true) : false;};
template<typename T> bool chmin(T &x, const T &y) {return (x > y)? (x = y, true) : false;};

int main(){
    int N;
    cin >> N;
    int A[N], B[N];
    rep(i, N) cin >> A[i];
    rep(i, N) cin >> B[i];
    vector<int> v1(N);
    iota(all(v1), 0);
    int a = 0, sum = 0;
    do{
        vector<int> v2(N);
        iota(all(v2), 0);
        do{
            int cnt = 0;
            rep(i, N){
                int e = v1[i], u = v2[i];
                if(A[e] > B[u]) cnt++;
                else cnt--;
            }
            if(cnt > 0) a++;
            sum++;
        } while(next_permutation(all(v2)));
    } while(next_permutation(all(v1)));
    cout << sp(10) << (ld)a/(ld)sum << endl;
}