Problem:
Score : 300 points

Problem Statement

You are given an integer N. Among the integers between 1 and N (inclusive), how many Shichi-Go-San numbers (literally "Seven-Five-Three numbers") are there?

Here, a Shichi-Go-San number is a positive integer that satisfies the following condition:

When the number is written in base ten, each of the digits 7, 5 and 3 appears at least once, and the other digits never appear.

Constraints

1 \leq N < 10^9

N is an integer.

Input

Input is given from Standard Input in the following format:

N

Output

Print the number of the Shichi-Go-San numbers between 1 and N (inclusive).

Sample Input 1

575

Sample Output 1

4

There are four Shichi-Go-San numbers not greater than 575: 357, 375, 537 and 573.

Sample Input 2

3600

Sample Output 2

13

There are 13 Shichi-Go-San numbers not greater than 3600: the above four numbers, 735, 753, 3357, 3375, 3537, 3557, 3573, 3575 and 3577.

Sample Input 3

999999999

Sample Output 3

26484

Solution in Python (3.4.3) (judge verdict: Accepted)

N = input().strip()

maxn = ()
base = set(['357', '375', '537', '573', '735', '753'])

if int(N) < 357:
  print(0)
else:
  for n in range(len(N) - 3):
    newb = set()
    for b in base:
      new3b = set([b[:i] + '3' + b[i:] for i in range(len(b) + 1)])
      new5b = set([b[:i] + '5' + b[i:] for i in range(len(b) + 1)])
      new7b = set([b[:i] + '7' + b[i:] for i in range(len(b) + 1)])
      newb |= new3b | new5b | new7b
    base |= newb
  print(len([i for i in base if int(i) <= int(N)]))