A =int(input())
list1 = [0]
p = 0
while True:
    list1.append(list1[0]+1)
    if A in list1:
        p=p+1
        list1.remove(A)
    list1.append(list1[0]+2)
    if A in list1:
        p=p+1
        list1.remove(A)
    x = filter((lambda y: y > A),list1)
    r=(list(x))
    if r:
        for i in r:
            list1.remove(i)
    del list1[0]
    if not list1:
        break
print(p)