Definition of Perfect number:

**A perfect number is a positive integer that is equal to the sum of its proper positive divisors**

**excluding**the number itself. By this definition, 1 is not a perfect number.

Explanation:

Take number 6.

Proper positive divisors of 6 is 1,2,3 and their sum is 1+2+3=6.

So, 6 is a perfect number.

So, 6 is a perfect number.

**Input: A single positive number x**

**Output:**

yes if given number x is a perfect number

yes if given number x is a perfect number

**no if given number x is not a perfect number**

Example 1:

Input: 6

Output: yes

Example 2:

Input: 7

Output: no**Implementation:**