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So'ngi izohlar

747. Sum
Vaqt limiti: 1 sekund
Xotira limiti: 64 MB

Your task is to find the sum of all integer numbers from 1 to N inclusive. 

Input

The input consists of a single positive integer N(1≤N≤4∙109).

Output

Write a single integer number that is the sum of all integer numbers from 1 to N inclusive

Samples

Input

Output

1

3

6

 

Tayyorladi: Azat Yusupov
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