x = int(input())
now = 0
ans = 0 

for i in range(101):
    now += 2
    ans += 2
    if (ans == x):
        break
    now += 2
    ans += 2
    if (ans == x):
        break
    now -= 1
    ans += 1
    if (ans == x):
        break
    now -= 1
    ans += 1
    if (ans == x):
        break
    now += 2
    ans += 2
    if (ans == x):
        break
    now -= 1
    ans += 1
    if (ans == x):
        break
    now -= 1
    ans += 1
    if (ans == x):
        break
    
print(ans)