N = int(input())


# N以下の753数を全列挙
def dfs(s):
  if int(s) > N:
    return 0
  ret = 1 if all(s.count(c) > 0 for c in '753') else 0
  for c in '753':
    ret += dfs(s + c)
  return ret
    
print(dfs('0'))
