from math import ceil, log

''' type checks since dealing with python '''

def revere_digits_forward(n):
	assert isinstance(n, int)
	sign = 1 if n >= 0 else -1
	n = abs(n)
	res = 0
	length = num_digits(n)
	for i in range(length):
		shift = length -1 - i
		first_digit = n // 10 ** shift
		res += first_digit * 10 ** i
		n %= 10 ** shift
	return sign * res

def num_digits(n):
	assert isinstance(n, int) and n >= 0
	# log(1) -> 0,
	# log(0) -> -inf
	return ceil(log(n) / log(10)) if n > 1 else 1


tests = [0, 1, 12345, 54321, -12345, -1]
for t in tests:
	print(t, revere_digits_forward(t))