#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <math.h>
#include <cmath>
#include <limits.h>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <functional>
#include <stdio.h>
using namespace std;

long long MOD = 1000000007;

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];
    }
    sort(A.begin(), A.end());
    sort(B.begin(), B.end());

    int sum = 0, a = 0;
    do {
        
        do {
            sum++;
            int cnt = 0;
            for (int i = 0; i < N; i++ ) {
                if (A[i] > B[i] ) { cnt++; }
            }
            if ( cnt > N/2 ) { a++; }            

        } while (next_permutation( B.begin(), B.end() ));

    } while (next_permutation( A.begin(), A.end() ));

    printf( "%.7f", static_cast<double>(a)/static_cast<double>(sum) );

    return 0;
}