#include <bits/stdc++.h>
using namespace std;

int main() {
    int N;
    cin >> N;
    vector<int> A(N), B(N);

    for(int i = 0; i < N; i++) {
        cin >> A[i];
    }
    for(int i = 0; i < N; i++) {
        cin >> B[i];
    }

    int nBattle = 0;
    int nWin = 0;

    vector<int> PermA(N), PermB(N);
    for(int i = 0; i < N; i++) {
        PermA[i] = i;
        PermB[i] = i;
    }

    do {
        do {
            int cntAWin = 0;
            for(int i = 0; i < N; i++) {
                if(A[PermA[i]] > B[PermB[i]]) {
                    cntAWin++;
                }
            }
            int BWin = N-cntAWin;
            if(cntAWin > BWin) {
                nWin++;
            }
            nBattle++;
        } while (next_permutation(PermB.begin(), PermB.end()));
    } while (next_permutation(PermA.begin(), PermA.end()));

    double Ans = 1.0 * nWin / nBattle;

    cout << Ans << endl;
}