Sum of internal angles of a Polygon

Given an integer N, the task is to find the sum of interior angles of an N-sided polygon. A plane figure having a minimum of three sides and angles is called a polygon.
Examples: 
 

Input: N = 3 
Output: 180 
3-sided polygon is a triangle and the sum 
of the interior angles of a triangle is 180.
Input: N = 6 
Output: 720 
 

Approach: The sum of internal angles of a polygon with N sides is given by (N - 2) * 180
Below is the implementation of the above approach:
 

540

Time Complexity: O(1)

Auxiliary Space: O(1)