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 <math.h>

char isUnder(long n,char a[]);
void adder(char a[]);
char is753(char a[]);

int main(void)
{
	long n,ans;
	char a[10]={};
	scanf("%ld",&n);

	a[0] = 7;
	a[1] = 5;
	a[2] = 3;

	ans = 0;
	while (isUnder(n,a)) {
		if (is753(a)) ans++;
		adder(a);
	}

	printf("%ld\n",ans);
	return 0;
}

char isUnder(long n,char a[])
{
	long ai=0;
	char i;
	for (i=0;i<10;i++) ai += a[i]*pow(10,i);
	if (n>=ai) return 1;
	return 0;
}

void adder(char a[])
{
	char i;
	for (i=0;i<10;i++) {
		a[i]+=(a[i]==0)?3:2;
		if (a[i]<=7) break;

		a[i]=3;
	}
	return;
}

char is753(char a[])
{
	char i,c[10]={};
	for (i=0;i<10;i++) {
		c[a[i]]++;
	}
	if (c[3]>0 && c[5]>0 && c[7]>0) return 1;
	else return 0;
}