#include<iostream>
#include<algorithm>
#include<cstdio>
using namespace std;
const int BUF = 5;


int N;
int val[2][BUF];

void read() {
    cin >> N;
    for (int i = 0; i < 2; ++i)
        for (int j = 0; j < N; ++j)
            cin >> val[i][j];
}


void work() {
    sort(val[0], val[0] + N);
    
    int nWin = 0;
    int nGame = 0;
    do {
        int cntWin = 0;
        for (int i = 0; i < N; ++i) {
            cntWin += val[0][i] > val[1][i];
        }
        nWin += cntWin > N / 2;
        ++nGame;
    } while(next_permutation(val[0], val[0] + N));

    printf("%.10lf\n", 1.0 * nWin / nGame);
}


int main() {
    read();
    work();
    return 0;
}