Problem Statement

There are $N$ children in AtCoder Kindergarten. Mr. Evi will arrange the children in a line, then give $1$ candy to the first child in the line, $2$ candies to the second child, ..., $N$ candies to the $N$-th child. How many candies will be necessary in total?

Constraints

• $1≦N≦100$

Input

The input is given from Standard Input in the following format:

$N$

Output

Print the necessary number of candies in total.

Sample Input 1

3

Sample Output 1

6

The answer is $1+2+3=6$.

Sample Input 2

10

Sample Output 2

55

The sum of the integers from $1$ to $10$ is $55$.

Sample Input 3

1

Sample Output 3

1

Only one child. The answer is $1$ in this case.