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: Runtime Error)

import math
def numberof753(n,used=set()):
    if n==0: return 1 if used=={7,5,3} else 0
    dig=math.ceil(math.log10(n))
    res=0
    if len(used)==0:
        res=sum(numberof753bydig(i) for i in range(1,dig))
    top=n//10**(dig-1)
    if top in (3,5,7):
        res+=numberof753(n%10**(dig-1),used.union({top}))
    if top>3:
        res+=numberof753bydig(dig-1,3-len(used.union({3})))
    if top>5:
        res+=numberof753bydig(dig-1,3-len(used.union({5})))
    if top>7:
        res+=numberof753bydig(dig-1,3-len(used.union({7})))
    return res
print(numberof753(int(input())))