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

int main() {
    int n;cin>>n;
    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 wins=0;
    int tot=0;
    int p[n];
    for (int i=0;i<n;i++)p[i]=i;
    do {
        int w=0;
        for (int i=0;i<n;i++) {
            if (a[p[i]] > b[i]) w++;
        }
        if (w > n/2) wins++;
        tot++;
    } while(next_permutation(p,p+n));
    cout<<fixed<<(double)wins/tot<<endl;
    return 0;
}