Begginers Guide - Exrcise. Help me, plz!

[Jeffrey-man]

Hello, everybody!
I'm a newbie and I'm just learning. I know, it's a stupid question, but I
want to resolve it.
Learning the Begginers Guide, I found an exercise. It tells me:
"Write a program that continually reads in numbers from the user and adds
them together until the sum reaches 100."
Can anybody help me?

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sum_stop = 100
num = input("Please enter the number: ")

for sum in range(num+num,sum_stop):
    print "Now the sum is", num+num
    sleep(1)

print "The sum is >/= 100!"

 -----

Maybe I'm doing something wrong?


Best regards.