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)

from collections import Counter
N = int(input())

def change_to_num(ls):
    ls = list(map(str, ls))
    strnum = ''.join(ls)
    return int(strnum)
def dfs(num_ls):
    '''
    引数のnum_ls以降の753numの総数を返す
    '''
    if change_to_num(num_ls) > N:
        return 0
    
    tmp = 0
    # 引数のnum_lsは753か？
    c = Counter(num_ls)
    is753 = True
    for num in [7,5,3]:
        if c[num] == 0:
            is753 = False
    if is753:
        tmp += 1
    
    # 次の状態の753総数を足す
    for num in [7,5,3]:
        num_ls.append(num)
        tmp += dfs(num_ls)
        num_ls.pop()
    return tmp
print(dfs([0]))