'''
cons(a, b) constructs a pair, and car(pair) and cdr(pair) returns the first and last element of that pair.
 For example, car(cons(3, 4)) returns 3, and cdr(cons(3, 4)) returns 4.

Given this implementation of cons:

def cons(a, b):
    def pair(f):
        return f(a, b)
    return pair
Implement car and cdr.
'''

def cons(a, b):
    def pair(f):
        return f(a, b)
    return pair


def car(a, b):
    return a


def cdr(a, b):
    return b


k = cons(3, 4)
print(k(car))
print(k(cdr))
