x = int(input())
ans = 0
now = 0
acc = 0
l = ["A","A","B","B","A","B","B"]
for i in range(100):
    for j in range(7):
        if l[j] == "A":
            now += 2
            acc += 2
        else:
            now -= 1
            acc += 1
        if now == x and ans == 0:ans = acc
        
print(ans)