Problem:
Score : 100 points

Problem Statement

You are given a positive integer N.
Find the minimum positive integer divisible by both 2 and N.

Constraints

1 \leq N \leq 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N

Output

Print the minimum positive integer divisible by both 2 and N.

Sample Input 1

3

Sample Output 1

6

6 is divisible by both 2 and 3.
Also, there is no positive integer less than 6 that is divisible by both 2 and 3.
Thus, the answer is 6.

Sample Input 2

10

Sample Output 2

10

Sample Input 3

999999999

Sample Output 3

1999999998

Solution in Python (3.4.3) (judge verdict: Runtime Error)

import math
import heapq
import sys
import re
from collections import Counter
import datetime
from decimal import Decimal, ROUND_HALF_UP, ROUND_HALF_EVEN

#N,K=map(int, input().split())  #複数数値入力　「A B」みたいなスペース空いた入力のとき
#x=list(map(int, input().split()))  #リスト入力 「a1 a2 a3 ...」みたいな配列のような入力のとき

def lcm(x, y):
    return (x * y) // math.gcd(x, y)

N=int(input())

print(lcm(2,N))