"This, might be an online judge, but it isn't meant to be played" - 『Sword Art Online Judge』, Programmers: Guanzhong Chen, Tudor Brindus, Timothy Li

Folklore

"Ahh… ha… uwahh!"

The sword swinging to these strange shouts swished around, cutting nothing but air.

Right afterwards, the blue user (which moved surprisingly quick considering its bulk) charged fiercely at its assailant. I burst into laughter, watching him fly through the air and roll on the hill after getting hit by the user's flat nose.

"Hahaha… not like that. The first movement is important, Java."

"Argh… that user."

The complaining assailant, a party member called Java, got up and glanced at me while answering plaintively.

"But C++, even if you say that… I can't do anything about the fact that it's moving."

I met this person, who had reddish hair held up by a bandana and simple leather armor worn over his thin body, a few hours ago. If he had revealed his real name, it would have been hard to omit the honorifics, but his name (Java) and mine (C++) were both names we had made up for our characters. Putting -san or -kun at the end of them would sound comical more than anything.

The legs of the person in question started shaking. What is this feeling that he's in a ridiculously pointless story made up for no reason?

Input Specification

~N~, ~1 \le N \le 10^9~.

Output Specification

Maybe, the sum of all the numbers from ~1~ to ~N~?