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  itertools
N = int(input())
N_len = len(str(N))

ans = 0
if N < 100:
    print(0)
for i in range(3,N_len+1):
    if i == N_len:
        l = list(itertools.product((3,5,7),repeat=N_len))
        ans += len(l)
        for s in l:
            a = int("".join(list(map(str,s))))
            if "3" not in str(a) or "5" not in str(a) or "7" not in str(a):
                ans -= 1
                continue
            if a > N:
                ans -= 1
        print(ans)

    else:
        ans += (3**i - 2**i*3 + 3)