from collections import deque
def solve():
  N = int(input())
  if N<=100:
    return N//3-3
  ans = 30
  d = deque(['0','3','6','9'])
  while len(d):
    s = d.popleft()
    if s[0]!='0':
      n = int(s)
      if n>100 and n<=N:
        ans += 1
    if len(s)<=len(str(N)):
      for l in ['0','3','6','9']:
        d.append(l+s)
  return ans
print(solve())