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>

int n, l_n;

int dfs(int a, int l, int t, int f, int s) {
	int ret0, ret3, ret5, ret7;
	if (l == l_n) return (t && f && s && a <= n) ? 1 : 0;
	ret0 = t && f && s;
	ret3 = dfs(10 * a + 3, l + 1, 1, f, s);
	ret5 = dfs(10 * a + 5, l + 1, t, 1, s);
	ret7 = dfs(10 * a + 7, l + 1, t, f, 1);
	return ret0 + ret3 + ret5 + ret7;
}

int len(int a) {
	return a > 9 ? len(a / 10) + 1 : 1;
}

int main(void) {
	scanf("%d", &n);
	l_n = len(n);
	printf("%d", dfs(0, 0, 0, 0, 0));
	return 0;
}