#include<bits/stdc++.h>
using namespace std;
#define N 4
#define rep(i,n) for(int i=0;i<n;i++)
int fact( int x ){
    int t = x;
    for(int i = 1;i < x-1;i++)t *= x-i;
    return t;
}
vector<int> num;
int ct = 0;//探索数
int row[24][N];
int ct2 = 0;

void narabikae(int n){
    rep(i,n){
        if(find(num.begin(),num.end(),i) == num.end()){
            num.push_back(i);
            ct++;
            if(ct == n){
                rep(j,n)row[ct2][j] = num[j];
                ct2++;
                num.pop_back();
                ct--;
            }
            else narabikae(n);
        }
    }
    num.pop_back();
    ct--;
}

bool battle(int *a,int *b,int x,int n){
    int win = 0;
    rep(i,n)if(a[row[x][i]] > b[i])win++;
    if(win > n/2)return 1;
    return 0;
}

int main(void){
    int n;
    int win = 0;
    cin >> n;
    int a[n];
    int b[n];
    rep(i,n)cin >> a[i];
    rep(i,n)cin >> b[i];
    narabikae(n);
    int n2 = fact(n);
    rep(i,n2)if(battle(a,b,i,n))win++;
    double ans = double(win)/n2;
    cout << ans << endl;
    return 0;
}