#include <algorithm>
#include <array>
#include <cmath>
#include <ctime>
#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 repb(i, e) for (int i = (int)(e); i >= 0; 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 vll = vector<long long>;
using vd = vector<double>;
using vvi = vector<vi>;
using vvll = vector<vll>;
using vvd = vector<vd>;
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 pli = pair<long long, int>;
using vpii = vector<pii>;
using vpll = vector<pll>;
using vpil = vector<pil>;
using vpli = vector<pli>;

const double PI = acos(-1);
const ll MOD = 1000000007;
const ll MODL = 2147483647;
const int INF = 1000000007;
const ll INFL = 1LL<<60;

template <typename T> inline bool chmin(T &a, T b) {if (a > b) {a = b; return true;} return false;}
template <typename T> inline bool chmax(T &a, T b) {if (a < b) {a = b; return true;} return false;}
// 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;}
inline void add(ll &a, ll b, ll m) {a = ((a % m + b % m)) % m;}
inline void sub(ll &a, ll b, ll m) {a = ((a % m - b % m) + m) % m;}
inline void mul(ll &a, ll b, ll m) {a = ((a % m) * (b % m)) % m;}


void dfs(int tmp, int num, int nw, int n, const vi &a, const vi &b, vi &dp) {
    if (num == n) {
        dp[nw]++;
        return;
    }
    rep(i, n) {
        if (tmp & (1<<i)) continue;
        if (a[num] < b[i]) dfs(tmp|(1<<i), num+1, nw, n, a, b, dp);
        else dfs(tmp|(1<<i), num+1, nw+1, n, a, b, dp);
    }
}


int main() {
    int n;
    double sumw = 0, suml = 0;
    cin >> n;
    vi a(n);
    vi b(n);
    rep(i, n) cin >> a[i];
    rep(i, n) cin >> b[i];
    vi dp(n+1, 0);
    dfs(0, 0, 0, n, a, b, dp);
    rep(i, n+1) {
        if (i > n-i) sumw += dp[i];
        else suml += dp[i];
    }
    cout << fixed << setprecision(10);
    cout << sumw / (sumw + suml) << endl;
}