def collatz(number):
    if number % 2 == 0:
        number = number // 2
        print(number)
        return number
    else:
        number = 3 * number + 1
        print(number)
        return number

print('Hello, we\'re going to explore the Collatz sequence!')
print('Please select a whole positive number.')

while True:
    collatzstart = (input())
    try:
        collatzstart = int(collatzstart)
        break
    except ValueError:
        print('That\'s not a whole positive number :(')
        print('Please try again.')

while collatzstart != 1:
    collatzstart = collatz(collatzstart)