ZOJ Problem Set - 1823
One of the central idea behind much cryptography is that factoring large numbers is computationally intensive. In this context one might use a 100 digit number that was a product of two 50 digit prime numbers. Even with the fastest projected computers this factorization will take hundreds of years.
You don't have those computers available, but if you are clever you can still factor fairly large numbers.
The input will be a sequence of integer values, one per line, terminated by a negative number. The numbers will fit in gcc's long long int datatype.
Each positive number from the input must be factored and all factors (other than 1) printed out. The factors must be printed in ascending order, and followed by a single blank line.
Source: University of Waterloo Local Contest 1996.09.28