I am have a problem with understanding a while loop, how to terminate it?

Question

How do I terminate an event-controlled while loop? say I have to write a program that does factorials for integers?
The way I did it was like this:

n = int(raw_input())
a = 0
while n !=0
    n = n-a
    print n*n
n = int(raw_input())

I thought the last line was going to terminate the loop by constantly updating n for every loop. And how do I make this to be one correct answer?

Answer 1

n = int(raw_input())
a = 1
while n !=0
    n = n-a
    print n*n
    a = a +1

Comments

This doesn't terminate and does not give a correct answer of a factorial.