X = int(input())

S = "AABBABB"
x = 0
i = 0
xx = 0
while True:
    if S[i] == 'A':
        x += 2
        xx += 2
    else:
        x -= 1
        xx += 1

    if x == X:
        break

    i += 1
    if i >= len(S):
        i = 0

print(xx)