#include <bits/stdc++.h>
// #include <atcoder/all> // NOTE: AtCoderライブラリ
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
using namespace std;
// using namespace atcoder; // NOTE: AtCoderライブラリ
typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<long long> vl;
typedef vector<bool> vb;
typedef vector<char> vc;
typedef pair<int, int> pii;
// #define INF __INT32_MAX__
#define INF 1e9
#define LINF __LONG_LONG_MAX__

int fac(int n) {
    if (n <= 1) return 1;
    return n * fac(n - 1);
}

int main() {
    int N; cin >> N;
    vi A(N);
    rep(i, N) cin >> A[i];
    vi B(N);
    rep(i, N) cin >> B[i];

    sort(A.begin(), A.end());
    sort(B.begin(), B.end());

    vector<vi> ap;
    do {
        vi tmp;
        rep(i, N) {
            tmp.push_back(A[i]);
        }
        ap.push_back(tmp);
    } while (next_permutation(A.begin(), A.end()));

    vector<vi> bp;
    do {
        vi tmp;
        rep(i, N) {
            tmp.push_back(B[i]);
        }
        bp.push_back(tmp);
    } while (next_permutation(B.begin(), B.end()));

    int awin = 0;
    for (int i = 0; i < ap.size(); i++) {
        vi app = ap[i];
        for (int j = 0; j < bp.size(); j++) {
            vi bpp = bp[j];

            int acnt = 0;
            int bcnt = 0;
            for (int k = 0; k < N; k++) {
                if (app[k] < bpp[k]) {
                    bcnt++;
                } else if (app[k] > bpp[k]) {
                    acnt++;
                }
            }

            if (acnt > bcnt) awin++;
        }
    }

    ld res = (1.0 * awin) / (1.0 * fac(N) * fac(N));

    cout << fixed << setprecision(10) << res << endl;
}