import sys
INPUT = sys.stdin.readline

def SINGLE_INT(): return int(INPUT())
def MULTIPLE_INT_LIST(): return list(map(int, INPUT().split()))
def MULTIPLE_INT_MAP(): return map(int, INPUT().split())
def SINGLE_STRING(): return INPUT()
def MULTIPLE_STRING(): return INPUT().split()

N = SINGLE_INT()

def is_integer_num(n):
    if isinstance(n, int):
        return True
    if isinstance(n, float):
        return n.is_integer()
    return False

if is_integer_num(N/2):
    print(N)
else:
    print(N*2)