words = ['tea', 'apple', 'dog', 'banana']
sorted_words = sorted(words, key=lambda w: (len(w), w[-1]))
print(sorted_words)

def fact(n):
    if n == 0:
        return 1
    return n * fact(n - 1)

print(fact(3))

def s(lst):
    if not lst:
        return 0
    return lst[0] + s(lst[1:])

print(s([1, 2, 3]))

def rev(s):
    if len(s) <= 1:
        return s
    return rev(s[1:]) + s[0]

print(rev("abc"))

def digits(n):
    if n < 10:
        return 1
    return 1 + digits(n // 10)

print(digits(1234))

def tail_sum(n, acc=0):
    if n == 0:
        return acc
    return tail_sum(n - 1, acc + n)

print(tail_sum(5))