#include <bits/stdc++.h>
#define rep(i, p, n) for (ll i = p; i < (ll)(n); i++)
#define rep2(i, p, n) for(ll i = p; i >= (ll)(n); i-- )
using namespace std;
using ll = long long;
double pi=3.141592653589793;
const long long inf=2*1e9;
const long long linf=8*1e18;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
//atcoder
#include <atcoder/modint>
#include <atcoder/dsu>
using namespace atcoder;
using mint1 = modint1000000007;
using mint2 = modint998244353;

int main() {
    ll N;
    cin >> N;
    vector<ll> A(N), B(N);
    rep(i, 0, N) {
        cin >> A.at(i);
    }
    rep(i, 0, N) {
        cin >> B.at(i);
    }
    vector<ll> P(0);
    rep(i, 0, N) {
        P.push_back(i);
    }
    ll ans=0;
    do {
        ll w=0;
        rep(i, 0, N) {
            if (A.at(i)>B.at(P.at(i))) {
                w++;
            }
        }
        if (w>N/2) {
            ans++;
        }
    }while(next_permutation(P.begin(), P.end()));
    ll b=1;
    rep(i ,0, N) {
        b*=(i+1);
    }
    double J=ans;
    J/=b;
    cout << J << endl;
}