Description

Please enter $n$, calculate the sum of natural numbers from $1$ to $n$ then output it.

Input Format

The line of input contains one integer,which is the number $n$.

Output Format

one integer,which is the sum of $1 + 2 + 3 + …… + n-1 + n$.

10

55

100

5050

Limit and hint

For $100\%$ testcases, $n\leq10^5$.