import sys
input = lambda: sys.stdin.readline().rstrip()

#  -----------------------  #

x = int(input())
ans = 0
now = 0
a = 0
while x != now:
  if a % 7 in {0, 1, 4}:
    ans += 2
    now += 2
  else:
    ans += 1
    now -= 1
  a += 1
print(ans)