Question: 
Write a function to check whether the given number is undulating or not.


Model's Code:
def is_undulating(number):
    for i in range(1, len(number) - 1):
        if not ((number[i] > number[i - 1] and number[i] > number[i + 1]) or (number[i] < number[i - 1] and number[i] < number[i + 1])):
            return False
    return True



Sample Correct Code:
def is_undulating(n): 
	if (len(n) <= 2): 
		return False
	for i in range(2, len(n)): 
		if (n[i - 2] != n[i]): 
			return False
	return True


Asserts:
assert is_undulating("1212121") == True
assert is_undulating("1991") == False
assert is_undulating("121") == True


Tests:
Test 1 of 3: PASS
Test 2 of 3: PASS
Test 3 of 3: PASS

Test 92 of 974: 70/92 (76.08695652173914%): success