import sys
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
mi = lambda: map(int, input().split())
li = lambda: list(mi())
INF = 2 ** 63 - 1
mod = 998244353

now = 0

s = 'aabbabb'
n = ii()
cnt = 0
for i in range(100):
    for v in s:
        if v == 'a':
            now += 2
            cnt += 2
        else:
            now -= 1
            cnt += 1
        if now == n:
            print(cnt)
            exit()