#-------------------------------------------------------------------------------
#  Collatz1.py
#-------------------------------------------------------------------------------

def Collatz(n):
   """Prints the 3n+1 sequence from n, terminating when it reaches 1 """
   while n != 1:
      print(n, end=", ")
      if n % 2 == 0:        # n is even
         n = n // 2
      else:                 # n is odd
         n = 3*n + 1
      # end if-else
   # end while
   print(n, end=".\n")
# end Collatz()


#-- main program --------------------------------------------------------------
  
k = int(input('Enter an integer: '))
print('The Collatz sequence starting at', k, 'is:')
Collatz(k)