n = int(input())
cnt = 0
ans = 0 
c = 0 

while True: 
    if (c % 7 in [0, 1, 4]): 
        cnt += 2
        ans += 2 
    else: 
        cnt -= 1 
        ans += 1 
    c += 1 
    if cnt == n: 
        break 

print(ans)