#include <bits/stdc++.h>

#define rep(i,a,b) for(int i=a;i<b;i++)
#define rrep(i,a,b) for(int i=a;i>=b;i--)
#define fore(i,a) for(auto &i:a)
#define all(x) (x).begin(),(x).end()
typedef long long ll; const int inf = INT_MAX / 2; const ll infl = 1LL << 60;

using namespace std;

int main(void)
{   
    int N=0;
    vector<int> A,B;
    int cnt=0,ans=0;
    cin >> N;
    A.resize(N);
    B.resize(N);

    int pa[4]={0,1,2,3},pb[4]={0,1,2,3};

    rep(i,0,N) cin >> A[i];
    rep(i,0,N) cin >> B[i];

    do{
        do{
            cnt++;
            int tmp=0;
            rep(i,0,N){
                if(A[pa[i]]>B[pb[i]])tmp++;
            }
            if(tmp>N/2)ans++;

        }while(next_permutation(pa,pa+N));

    }while(next_permutation(pb,pb+N));

    printf("%.10f\n",(double)ans/(double)cnt);

    return 0;
}