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)

import bisect

n = int(input())
k = len(str(n))

k753_num = []
def get_k753_num(k, s):
  if k == 0:
    if "7" in s and "5" in s and "3" in s:
      k753_num.append(int(s))
      return True
    else:
      return False
  pata = get_k753_num(k-1, "7" + s)
  patb = get_k753_num(k-1, "5" + s)
  patc = get_k753_num(k-1, "3" + s)
  
def count_k753_num(k):
  if k<3:
    return 0
  else:
    return 3**k - (2**k * 3) + 3

# count up k-1 753 num
count = 0
for i in range(k):
  count += count_k753_num(i)

# add k 753 num
get_k753_num(k, "")
k753_num.sort()
count += bisect.bisect_right(k753_num, n)

print(count)