#include <bits/stdc++.h>
//#include <atcoder/all>
#define rep(i, n) for (int i = 0; i < (n); i++)
using ll = long long;
using namespace std;
//using namespace atcoder;
const int mod = 1e7+7;
const int INF =1e9+1;
int n;
vector<int> a,b;
vector<bool> flag1,flag2;
int win=0, match=0;
void dfs(vector<int> x,vector<int> y){
    if(x.size()==n){
        match++;
        int tmp1=0,tmp2=0;
        rep(i,n){
            if(x[i]>y[i])tmp1++;
            else if(x[i]<y[i])tmp2++;
        }
        if(tmp1>tmp2)win++;
        return ;
    }
    for(int i=0;i<n;i++){
        if(flag1[i]==1)continue;
        x.push_back(a[i]);flag1[i]=1;
        rep(j,n){
            if(flag2[j]==1)continue;
            y.push_back(b[j]);flag2[j]=1;
            dfs(x,y);
            y.pop_back();flag2[j]=0;
        }
        x.pop_back(); flag1[i]=0;
    }
}
 
 
int main() {
    cin>>n;
    a=b=vector<int> (n);
    flag1=flag2=vector<bool>(n,0);
    rep(i,n)cin>>a[i];
    rep(i,n)cin>>b[i];
    dfs(vector<int>(0),vector<int>(0));
    cout<<fixed<<setprecision(15);
    cout<<(double)win/match<<endl;
}