#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

#define RREP(i,s,e) for (i = e-1; i >= s; i--)
#define rrep(i,n) RREP(i,0,n)
#define REP(i,s,e) for (i = s; i < e; i++)
#define rep(i,n) REP(i,0,n)
#define INF 1e8

double dfs(vector<int>& a, vector<int>& b, int cnt) {
    int i, j, ret = 0;
    if (a.empty())
        return cnt > 0;
    rep (i,a.size()) rep (j,b.size()) {
        auto x = a;
        auto y = b;
        int c = cnt;
        x.erase(x.begin()+i);
        y.erase(y.begin()+j);
        c += (a[i] > b[j]) - (a[i] < b[j]);
        ret += dfs(x,y,c);
    }
    return ret;
}

int main() {
    int n, i, total = 1;
    double ans;
    vector<int> a,b;
    cin >> n;
    a.resize(n);
    b.resize(n);
    rep (i,n) cin >> a[i];
    rep (i,n) cin >> b[i];
    rep (i,n) total *= i+1;
    total *= total;
    ans = dfs(a,b,0) / total;
    cout << ans << endl;
    return 0;
}