Sum of Unique Factors

Given a positive integer \( n \), your task is to compute the sum of all its unique factors. A factor is a number that divides \( n \) evenly. For example, if \( n = 12 \), the factors are \( 1, 2, 3, 4, 6, 12 \), and their sum is \( 28 \). If \( n \) is not a positive integer (i.e. \( n \le 0 \)), you should output "None".

Note: Each factor should be counted only once, even if it appears as a product in a pair (for example, if \( n \) is a perfect square, its square root should only be counted once).

inputFormat

The input consists of a single line containing an integer \( n \).

outputFormat

If \( n \) is a positive integer, output an integer representing the sum of its unique factors. Otherwise, output "None".

12

28