Rules :

1. if a number is even ; / 2

2. if a number is odd ; *3+1

3.if a number reaches 1 , stop

##————————————————————————————————-

inputnum = raw_input (“please inter a positive number : “)
number = int (inputnum)
if number <= 0 :
print “You must enter a positive number”,
elif number!= 1 :
print “Start countdown : ”
while number != 1 :
if number == 2 :
print number, “==> 1 “,
break
elif number % 2 == 0 :
print number, “==>”,
number = number / 2
elif number % 2 != 0 :
print number, “==>” ,
number = number * 3 + 1
print “==> End”
elif number ==1 :
print number, “==> End”