#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, s, e) for (int i = (int)(s); i < (int)(e); ++i)
#define all(a) (a).begin(),(a).end()

int main() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    
    int N;
    cin >> N;
    vector<int> A(N), B(N);
    rep(i, 0, N) cin >> A[i];
    rep(i, 0, N) cin >> B[i];
    
    sort(all(A));
    sort(all(B));
    
    ll win = 0;
    do {
        do {
            int cnt = 0;
            rep(i, 0, N) if (A[i] > B[i]) ++cnt;
            if (cnt*2 > N) ++win;
        } while (next_permutation(all(B)));
    } while (next_permutation(all(A)));
    
    ll t = 1;
    rep(i, 1, N + 1) t *= i;
    cout << fixed << setprecision(10) << (double)win / (double)(t*t) << '\n';
}