#include<iostream>
#include<algorithm>
#include<vector>
#include<cmath>
#include<utility>
#include<cstdio>
#include<set>
#include<string>
#include<map>
#include<queue>
#include<stack>
using namespace std;
#define rep(i,x,n) for(int i=x;i<n;i++)
using ll=long long;
typedef pair<int,int> P;
string s;
int k;
int INF=1000000000;
int dh[4]={0,1,0,-1};
int dw[4]={1,0,-1,0};

int main(){
    int n;cin>>n;
    int a[n],b[n];
    rep(i,0,n)cin>>a[i];
    rep(i,0,n)cin>>b[i];
    sort(a,a+n);
    sort(b,b+n);
    int wina=0;
    int game=0;
    do{
        int pa=0,pb=0;
        rep(i,0,n){
            if(a[i]>b[i]) pa++;
            else pb++;
        }
        if(pa>pb) wina++;
        game++;
    }while(next_permutation(a,a+n));
    double ans=(double)wina/(double)game;
    printf("%.8f\n",ans);
}