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>

long long int n;

long long int dfs(long long int s){
  long long int ret, t, f1, f2, f3;

  if (s > n) {
    return 0;
  }

  t = s;
  f1 = 0;
  f2 = 0;
  f3 = 0;
  while (t > 0) {
    if (t % 10 == 7) {
      f1 = 1;
    }
    if (t % 10 == 5) {
      f2 = 1;
    }
    if (t % 10 == 3) {
      f3 = 1;
    }
    t = t / 10;
    if (f1 == 1 && f2 == 1 && f3 == 1) {
      break;
    }
  }
  if (f1 == 1 && f2 == 1 && f3 == 1) {
    ret = 1;
  }
  else {
    ret = 0;
  }
  ret += dfs(s*10 + 7);
  ret += dfs(s*10 + 5);
  ret += dfs(s*10 + 3);
  return ret;
}

int main(void){

  scanf("%lld", &n);

  printf("%lld\n", dfs(0));

  return 0;
}