#include<bits/stdc++.h>

#define _GLIBCXX_DEBUG
#define all(v) (v).begin(),(v).end()

using namespace std;

using ll=long long;
using pii=pair<int, int>;
using vi=vector<int>;
using vii=vector<vector<int>>;

const ll LINF=1LL<<60;
const int INF=1<<29;
const int MOD=1e9+7;

int main(){
    int N; cin >> N;
    vi a(N), b(N);
    for(auto &x : a) cin >> x;
    for(auto &x : b) cin >> x;
    vi ord1(N), ord2(N);
    for(int i=0; i<N; i++){
        ord1[i]=i;
        ord2[i]=i;
    }
    int cnt=0, win=0;
    do{
        do{
            cnt++;
            int k=0;
            for(int i=0; i<N; i++){
                if(a[ord1[i]] > b[ord2[i]]) k++;
            }
            if(k > N-k) win++;
        }while(next_permutation(all(ord2)));
    }while(next_permutation(all(ord1)));
    cout << fixed << setprecision(4) << (double)win/cnt << endl;
    return 0;
}