// T(n, k) = T(n - k0, k) + T(n, {k1..k})

def countChange(money: Int, coins: List[Int]): Int = {
    if (money < 0 || coins.isEmpty) 0
    else if (money == 0) 1
    else countChange(money - coins.head, coins) + countChange(money, coins.tail)
}