Count Unique Pairs among Employees

You are given the number of employees N. Your task is to compute the total number of unique pairs that can be formed among these employees. Each pair is formed by choosing 2 employees out of N, and the formula to compute the number of pairs is given by: $$\frac{N\times (N-1)}{2}$$.

If there are less than 2 employees, it is impossible to form a pair, so the answer should be 0.

inputFormat

The input is a single integer N (read from stdin) which represents the number of employees.

outputFormat

Output a single integer (to stdout) representing the total number of unique pairs that can be formed among the employees.## sample

4

6