#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,n) for (int i=a;i<n;i++)
#define per(i,a,n) for (int i=n-1;i>=a;i--)
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
typedef vector<int> VI;
typedef long long ll;
typedef pair<int,int> PII;
typedef double db;
mt19937 mrand(random_device{}()); 
const ll mod=998244353;
int rnd(int x) { return mrand() % x;}
ll powmod(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
ll gcd(ll a,ll b) { return b?gcd(b,a%b):a;}
// head

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);

    int N;
    cin >> N;
    VI A(N), B(N), ord(N);
    rep(i, 0, N) cin >> A[i];
    rep(i, 0, N) cin >> B[i];
    iota(all(ord), 0);
    int cnt = 0, a_cnt = 0;
    do {
        int a_win = 0, b_win = 0;
        rep(i, 0, N) {
            a_win += A[ord[i]] > B[i];
            b_win += B[ord[i]] < B[i];
        }
        a_cnt += a_win > b_win;
        ++cnt;
    } while (next_permutation(all(ord)));

    cout << (double)a_cnt / cnt << endl;

    return 0;
}