#000237

Sum All Numbers

Your task is to find the sum of all integer numbers lying between 1 and N inclusive.



InputThe input consists of a single integer N that is not greater than (UNKNOWN) by it's absolute value.


OutputWrite to the output a single integer number that is the sum of all integer numbers lying between 1 and N inclusive.


Input:
2
Output:
3



Input:
-3
Output:
-5

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