Write a program that sums all integers from 1 to N.

Subtask	Points	Additional Constraints
1	40	$1 \leq n \leq 10^3$
2	60	$1 \leq n \leq 10^9$

The program is given one integer $n (1 \leq n \leq 10^9)$ .

Output one integer - the sum of all numbers from 1 to $n$ .

Мисол 1

Вуруд

Баромад

Arithmetic sum