A. Ana, Hooray for Mariana!
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output

Mariana Counts $$$1$$$ is a song often used while children are learning to count, since it presents counting in a didactic and playful way. For older children, the song was generalized into Mariana Counts $$$X$$$ (where $$$X$$$ is a natural number), and goes as follows:

Mariana counts $$$1$$$
Mariana counts $$$1$$$: it is $$$1$$$, it is Ana
Hooray for Mariana, hooray for Mariana!
Mariana counts $$$2$$$
Mariana counts $$$2$$$: it is $$$1$$$, it is $$$2$$$, it is Ana
Hooray for Mariana, hooray for Mariana!
$$$\ldots$$$
Mariana counts $$$X$$$
Mariana counts $$$X$$$: it is $$$1$$$, it is $$$2$$$, ..., it is $$$X$$$, it is Ana
Hooray for Mariana, hooray for Mariana!

To measure its didactic value, print how many numbers appear in the song.

Input

The input consists of a single integer $$$X\ (1 \leq X \leq 1000)$$$.

Output

The output should contain a single integer: how many numbers were counted in the song.

Examples
Input
2
Output
7
Input
5
Output
25
Input
10
Output
75
Note

Explanation for example 1

Mariana counted $$$7$$$ numbers: four times the number $$$1$$$ and three times the number $$$2$$$, as can be seen in the first two stanzas of the statement.