#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) for(int i=0;i < (n);i++)
#define ALL(obj) (obj).begin(),(obj).end()
#define SCANF(i) int i;scanf("%d",&i)
using namespace std;
using P = pair<int,int>;
const long long INF = 1LL << 60;
const int IINF=100000000;
const int MOD = (int)1e9 + 7;
typedef long long ll;
//約数列挙
vector<long long> divisor(long long n) {
    vector<long long> ret;
    for (long long i = 1; i * i <= n; i++) {
        if (n % i == 0) {
            ret.push_back(i);
            if (i * i != n) ret.push_back(n / i);
        }
    }
    //sort(ret.begin(), ret.end()); // 昇順に並べる
    return ret;
}
vector<int> dx={1,0,-1,0};vector<int> dy={0,-1,0,1};

signed main () {
    int n;cin >> n;
    vector<int> lista(n);vector<int> listb(n);
    REP(i,n)cin >> lista[i];REP(j,n)cin >> listb[j];
    sort(ALL(lista));sort(ALL(listb));
    double cnt = 0;double allcnt = 0;
    do{
        do{
            int tmpcnt = 0;
            REP(i,n){
                if(lista[i]>listb[i])tmpcnt++;
            }
            if(n-tmpcnt<tmpcnt)cnt++;
            allcnt++;
        }while(next_permutation(ALL(listb)));
    }while(next_permutation(ALL(lista)));
    double ans = cnt / allcnt; 
    cout << ans << endl;
}