#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>

#define FORR(i,b,e) for(int i=(b);i<(int)(e);++i)
#define FOR(i,e) FORR(i,0,e)
#define dump(var) cerr << #var ": " << var << "\n"
#define dumpc(con) for(auto& e: con) cerr << e << " "; cerr<<"\n"

typedef long long ll;
typedef unsigned long long ull;

const double EPS = 1e-6;
const int d4[] = {0, -1, 0, 1, 0};

using namespace std;


int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    int N;
    cin >> N;
    vector<int> A(N), B(N);
    FOR(i, N) cin >> A[i];
    FOR(i, N) cin >> B[i];

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

    int win = 0, pat = 0;
    do {
        sort(B.begin(), B.end());
        do {
            pat++;
            int aw = 0;
            FOR(i, N) aw += (A[i] > B[i]);
            win += (aw > N/2);
        }
        while (next_permutation(B.begin(), B.end()));
    }
    while (next_permutation(A.begin(), A.end()));

    cout << fixed << setprecision(3)
         << (double)win / (double)pat << endl;

    return 0;
}