#include <bits/stdc++.h>
using namespace std;
using C = complex<double>;
const int mod = 998244353;
const long long LINF = 1001002003004005006;
const int INF = 1001001001;
const double PI = acos(-1);
const double EPS = 1e-10;
const int di[4] = {-1,0,1,0};
const int dj[4] = {0,-1,0,1};
const int dx[8] = {1,1,1,0,0,-1,-1,-1};
const int dy[8] = {1,0,-1,1,-1,1,0,-1};
# define sz(x) (int)(x).size()
# define rsz(x,n) x.resize(n)
# define yosupo(x) {cout << (x) << endl; return 0;}
# define ll long long
# define fi first
# define se second
# define pb push_back
# define pf push_front
# define eb emplace_back
# define ef emplace_front
# define pob pop_back
# define pof pop_front
# define GET_MACRO(_1, _2, _3, NAME, ...) NAME
# define _rep(i, n) _rep2(i, 0, n)
# define _rep2(i, a, b) for(int i = (int)(a); i < (int)(b); i++)
# define rep(...) GET_MACRO(__VA_ARGS__, _rep2, _rep)(__VA_ARGS__)
# define srep(i, a, b) for(int i = a; i <= b; ++i)
# define all(obj) (obj).begin(), (obj).end()
# define rall(obj) (obj).rbegin(), (obj).rend()
inline void YesNo(bool f) { std::cout << (f? "Yes": "No") << std::endl; }
void read() {}
template <typename T, class... U> void read(T &t, U &...u) { cin >> t; read(u...); }
void writeln() { cout << endl; }
template <typename T, class... U, char sep = ' '> void writeln(const T &t, const U &...u) { cout << t; if (sizeof...(u)) cout << sep; writeln(u...); }
# define Pll pair<ll, ll>
# define P pair<int,int>
# define bit(x,i) (((x) >> (i)) & 1)
# define equals(a, b) (fabs((a) - (b)) < EPS) // 誤差を考慮した同値判定
template<class T>bool chmax(T &a, const T &b) { if (a < b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b < a) { a = b; return 1; } return 0; }
template<typename T>istream& operator>>(istream&i,vector<T>&v){rep(j,v.size())i>>v[j];return i;}
template<typename T>string join(vector<T>&v){stringstream s;rep(i,v.size())s<<' '<<v[i];return s.str().substr(1);}
template<typename T>ostream& operator<<(ostream&o,vector<T>&v){if(v.size())o<<join(v);return o;}
template<typename T>ostream& operator<<(ostream&o,vector<vector<T>>&vv){if(vv.size())o<<join(vv);return o;}
template <class T, class U> ostream& operator<<(ostream& os, const pair<T, U>& p) { return os << "P(" << p.first << " " << p.second << ")";}
template<typename T> using vc = vector<T>;
template<typename T> using vv = vc<vc<T>>;
using vi = vc<int>; using vvi = vv<int>;
using vl = vc<ll>; using vvl = vv<ll>;

void solve() {
    int n;
    read(n);
    vi a(n), b(n);
    rep(i,n) read(a[i]);
    rep(i,n) read(b[i]);
    vi perm1(n), perm2(n);
    iota(all(perm1),0);
    iota(all(perm2),0);
    int cnt = 0, tot = 0;
    do{
        do{
            int cntA = 0, cntB = 0;
            rep(i,n) {
                if(a[perm1[i]] > b[perm2[i]]) cntA++;
                else cntB++;
            }
            if(cntA > cntB) cnt++;
            tot++;
        }while(next_permutation(all(perm2)));
    }while(next_permutation(all(perm1)));
    double ans = (double)cnt/tot;
    printf("%.10lf\n", ans);
}

int main() {
    int tt = 1;
    //read(tt);
    while(tt--) {
        solve();
    }
}