Problem Description

Given a positive integer $n$, compute the cumulative sum of the following form:

$1 + (1+2) + (1+2+3) + (1+2+3+4) + \cdots + (1+2+3+4+5+ \cdots +n)$.

Input Format

Input consists of a single positive integer $n$. It is guaranteed that $1 < n \leq 100$.

Output Format

Output the result of the cumulative sum.

Sample Input and Output

Sample Input #1

3

Sample Output #1

10

Sample Input #2

4

Sample Output #2

20

Sample Input #3

10

Sample Output #3

220

见题面 Input 部分

见题面 Output 部分