#include <bits/stdc++.h>
#define For(i, a, b) for(int i = a; i < b; i++)
#define rep(i, n) For(i, 0, n)
#define rFor(i, a, b) for(int i = a; i >= b; i--)
#define ALL(v) (v).begin(), (v).end()
#define rALL(v) (v).rbegin(), (v).rend()
using namespace std;

using lint = long long;
using ld = long double;

int INF = 2000000000;
lint LINF = 1000000000000000000;

int main() {
    int n;
    cin >> n;
    vector<int> a(n);
    rep(i, n) {
        cin >> a[i];
    }
    vector<int> b(n);
    rep(i, n) {
        cin >> b[i];
    }
    vector<int> x(n);
    rep(i, n) {
        x[i] = i;
    }
    ld all = 0, win = 0;
    do {
        vector<int> y(n);
        rep(i, n) {
            y[i] = i;
        }
        do {
            all++;
            int ca = 0, cb = 0;
            rep(i, n) {
                if (a[x[i]] > b[y[i]]) {
                    ca++;
                } else if (a[x[i]] < b[y[i]]) {
                    cb++;
                }
            }
            if (ca > cb) {
                win++;
            }
        } while (next_permutation(ALL(y)));
    } while (next_permutation(ALL(x)));
    cout << fixed << setprecision(10) << win / all << endl;
}