#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
const int INF=10000000;

int main(){  

    ios::sync_with_stdio(false);
    cin.tie(nullptr);
   
    int N;
    cin>>N;
    vector<int> Acard(N);
    vector<int> Bcard(N);
    rep(i,N){
        cin>>Acard[i];
    }
    rep(i,N){
        cin>>Bcard[i];
    }
    double res=0;
    sort(Bcard.begin(),Bcard.end());
    do{
    int sum=0;
    rep(i,N){
        if(Acard[i]>Bcard[i]) sum++;
    }
    if(sum>N/2) res++;

    }while(next_permutation(Bcard.begin(),Bcard.end()));
  
    double all=1;
    for(int i=N;i>0;i--){
        all*=i;
    }

    cout<<res/all<<endl;

}