#include <bits/stdc++.h>
using namespace std;
//#include <atcoder/all>
//using namespace atcoder;
using ll = long long;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
#define all(A) A.begin(),A.end()
#define rep(i, n) for (ll i = 0; i < (ll) (n); i++)
template<class T>
bool chmax(T& p, T q, bool C = 1) {
    if (C == 0 && p == q) {
        return 1;
    }
    if (p < q) {
        p = q;
        return 1;
    }
    else {
        return 0;
    }
}

template<class T>
bool chmin(T& p, T q, bool C = 1) {
    if (C == 0 && p == q) {
        return 1;
    }
    if (p > q) {
        p = q;
        return 1;
    }
    else {
        return 0;
    }
}

ll modPow(long long a, long long n, long long p) {
    if (n == 0) return 1; // 0乗にも対応する場合
    if (n == 1) return a % p;
    if (n % 2 == 1) return (a * modPow(a, n - 1, p)) % p;
    long long t = modPow(a, n / 2, p);
    return (t * t) % p;
}


ll gcd(ll(a), ll(b)) {
    if (a == 0)return b;
    if (b == 0)return a;
    ll c = a;
    while (a % b != 0) {
        c = a % b;
        a = b;
        b = c;
    }
    return b;
}
ll sqrtz(ll N) {
    ll L = 0;
    ll R = sqrt(N) + 10000;
    while (abs(R - L) > 1) {
        ll mid = (R + L) / 2;
        if (mid * mid <= N)L = mid;
        else R = mid;
    }
    return L;

}


/*
using mint = modint998244353;
using vm = vector<mint>;
using vvm = vector<vm>;
using vvvm = vector<vvm>;
*/
vector<ll> fact, factinv, inv;
const ll mod = 998244353;
void prenCkModp(ll n) {
    fact.resize(n + 5);
    factinv.resize(n + 5);
    inv.resize(n + 5);
    fact[0] = fact[1] = 1;
    factinv[0] = factinv[1] = 1;
    inv[1] = 1;
    for (ll i = 2; i < n + 5; i++) {
        fact[i] = (fact[i - 1] * i) % mod;
        inv[i] = ((mod - ((inv[mod % i] * (mod / i))) % mod) + mod) % mod;
        factinv[i] = (factinv[i - 1] * inv[i]) % mod;
    }
}
ll nCk(ll n, ll k) {
    if (n < k || k < 0) return 0;
    return (fact[n] * ((factinv[k] * factinv[n - k]) % mod)) % mod;
}

bool P(string T) {
    ll N = T.size();
    rep(i, N)if (T[i] != T[N - 1 - i])return false;
    return 1;
}

struct fenwick_tree {
    ll n;
    vll bit;
    fenwick_tree(ll num) :bit(num + 1, 0) { n = num; }

    void add(ll i, ll w) {
        for (ll x = i + 1; x <= n; x += x & -x) {
            bit[x - 1] += w;
        }
    }

    ll sum(ll i) {
        ll ret = 0;
        for (ll x = i + 1; x > 0; x -= x & -x) {
            ret += bit[x - 1];
        }
        return ret;
    }

    ll sum(ll L, ll R) {
        return sum(R) - sum(L);
    }


};
ll TE(vll A) {
    ll res = 0;
    ll N = A.size();
    fenwick_tree fw(N);
    rep(i, N) {
        res += i - fw.sum(A[i]);
        fw.add(A[i], 1);
    }
    return res;
}

int main() {

    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    ll N;
    cin>>N;
    vll A(N),B(N);
    rep(i,N)cin>>A[i];
    rep(i,N)cin>>B[i];
    ll p=0,q=0;
    sort(all(A));
    sort(all(B));
    do{
        sort(all(B));
        do{
            ll cnt=0;
            rep(i,N){
                if(A[i]>B[i])cnt++;
            }
            if(cnt>N-cnt)q++;
            p++;
        }while(next_permutation(all(B)));
    }while(next_permutation(all(A)));
    cout<<fixed<<setprecision(16)<<double(q)/double(p)<<endl;

}