#include <algorithm>
#include <array>
#include <cmath>
#include <deque>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep2(i, s, n) for (int i = (int)(s); i < (int)(n); i++)
#define all(x) x.begin(), x.end()
using namespace std;
using ll = long long;
using ull = unsigned long long;
using vi = vector<int>;
using vl = vector<long>;
using vll = vector<long long>;
using vvi = vector<vi>;
using vvl = vector<vl>;
using vvll = vector<vll>;
using vs = vector<string>;
using vb = vector<bool>;
using vvb = vector<vb>;
using vc = vector<char>;
using vvc = vector<vc>;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pil = pair<int, long long>;
using vpii = vector<pii>;
template <typename T> T gcd(T a, T b) {if (a < b) swap(a, b); if (b == 0) return a; else return gcd(b, a%b);}
template <typename T> inline T ceil(T a, T b) {return (a+(b-1))/b;}
template <typename T> inline T floor(T a, T b) {return a/b;}

const double PI = 3.141592653589793238;
const ll MOD = 1000000007;
const ll MODL = 2147483647;
const int INF = 1000000007;
const ll INFL = 1LL<<60;


int main() {
    int n, score1, score2;
    double s1, s2;
    cin >> n;
    vi a(n);
    vi b(n);
    rep(i, n) cin >> a[i];
    rep(i, n) cin >> b[i];
    vi id(n);
    iota(all(id), 0);
    s1 = 0;
    s2 = 0;
    do {
        score1 = 0;
        score2 = 0;
        rep(i, n) {
            if (a[i] > b[id[i]]) score1++;
            else score2++;
        }
        if (score1 > score2) s1 += 1;
        else s2 += 1;
    } while (next_permutation(all(id)));
    cout << fixed << setprecision(10);
    cout << s1 / (s1+s2) << endl;
}