def countTwoDigit(N):
  count = 0
  lim = min(99, int(N))
  for i in range(10, lim+1):
    if (i//10 + i%10)%3==0:
      count += 1
  return count

def countLittleDigit(N):
  L = len(N)
  if L<=2:
    return 0
  return pow(4, L-1) - pow(4, 2)

def countSameDigit(N):
  L = len(N)
  if L<=2: return 0
  count = 0
  for i in range(L):
    digit = int(N[i])
    if digit == 0: continue
    times = (digit-1)//3
    count += pow(3, L-1-i) * times
    if digit%3 != 0: break
  else:
    if int(N)%3==0:
      count += 1
  return count

N = input()
L2 = countTwoDigit(N)
L3 = countLittleDigit(N)
L4 = countSameDigit(N)
print(L2+L3+L4)