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

int N;
int main() {
    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;
    int cnt = 0;
    do {
        do {
            int win = 0;
            for(int i=0; i<N; i++)if(A[i] > B[i]) win++;
            if(win*2>N) cnt++;
            sum++;
        }while(next_permutation(B.begin(), B.end()));
    }while(next_permutation(A.begin(), A.end()));
    cout<<(double)cnt / (double)sum<<endl;
}