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 C (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>
#include <stdint.h>
#include <stdbool.h>
int64_t N;

int64_t search(int64_t n, bool seven, bool five, bool three) {
  if(n > N) {
    return 0;
  }
  
  int ret0 = search(n*10 + 7, true, five, three);
  int ret1 = search(n*10 + 5, seven, true, three);
  int ret2 = search(n*10 + 3, seven, five, true);
  int ret3 = 0;
  if(seven && five && three)
    ret3 = 1;
  return ret0 + ret1 + ret2 + ret3;
}

int main(void) {
  scanf("%ld", &N);
  printf("%ld\n", search(0, false, false, false));
  return 0;
}