Even Sum

By Kay Akashi

Time: 1000 ms

Memory: 256000 kB

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Problem Statement

Given an even positive number $n$ , output the sum of even positive numbers smaller than or equal to $n$ .

$0 \leq n \leq 10^{5}$ .

The input consists of one number $n$ .

Output the answer.

The even positive numbers smaller than or equal to $2$ is $2$ itself, only. Hence, the answer is $2$ .

The even positive numbers smaller than or equal to $10$ are $2$ , $4$ , $6$ , $8$ , and $10$ . Hence, the answer is $2 + 4 + 6 + 8 + 10 = 30$ .