#include<bits/stdc++.h>
typedef long long ll;
using namespace std;
int INF = 1e9;
int MOD = 1e9+7;
int fact(int n){
    if(n == 1)return 1;
    return n*fact(n-1);
}
main(){
    int N;
    cin >> N;
    vector<int>A,B;
    for(int i = 0;i < N;i++){int a;cin >> a;A.push_back(a);}
    for(int i = 0;i < N;i++){int a;cin >> a;B.push_back(a);}
    sort(A.begin(),A.end());
    sort(B.begin(),B.end());
    int v = 0;
    do{
        do{
            int cnt = 0;
            for(int i = 0;i < N;i++){
                if(A[i] > B[i])cnt++;
                else cnt--;
            }
            if(cnt > 0)v++;
        }while(next_permutation(B.begin(),B.end()));
    }while(next_permutation(A.begin(),A.end()));
    cout << 1. * v / (fact(N)*fact(N)) << endl;;
}