#include "bits/stdc++.h"
using namespace std;
#define FOR(i,a,b) for(int i =(a);i<(b);i++)
#define REP(i,n) for(int i=0;i<(n);i++)
#define REPm(i,n) for(int i=(n)-1;i>=0;i--)
#define REP1(i,n) for(int i=1;i<=(n);i++)
#define mp make_pair
typedef long long ll;
int main(){
    int N;
    cin >> N;
    vector<int> A(N),B(N);
    REP(i,N) cin >> A[i];
    REP(i,N) cin >> B[i];
    int ans = 0;
    sort(B.begin(),B.end());
    do{
        int win = 0;
        int lose = 0;
        REP(i,N){
            if(A[i] > B[i]) win++;
            else lose++;
        }
        if(win > lose) ans++;
    }while(next_permutation(B.begin(),B.end()));
    int all = 1;
    REP1(i,N) all *= i;
    double p = ((double)ans)/all;
    printf("%.10f\n",p);
    return 0;
}