Sum Problem

TimeLimit: 1000/500 MS (Java/Others) MemoryLimit: 65536/32768 K (Java/Others)

64-bit integer IO format:%I64d

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Problem Description

In this problem, your task is to calculate SUM(n) = 1 + 2 + 3 + ... + n.

Input

The input will consist of a series of integers n, one integer per line.

Output

For each case, output SUM(n) in one line, followed by a blank line. You may assume the result will be in the range of 32-bit signed integer.

SampleInput

1
100

SampleOutput

1

5050

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