Given an integer N, find the sum of all the numbers from 1 to N inclusive

Example 1

Input

1

Output

1

Explanation

The sum of all numbers from 1 to 1 = 1

Example 2

Input

5

Output

15

Explanation

The sum of all the numbers from 1 to 5 =
1 + 2 + 3 + 4 + 5 = 15

Example 3

Input

3

Output

6

Explanation

The sum of all the numbers from 1 to 3 =
1 + 2 + 3 = 6