import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt(),i,c=0;
		for(i=1;i<=n;i++) {
			if(i%10 == 0 && i/10%10!= 0) {
				c++;
			}
			if(i/10 >=10 && i/10%10 == 0 && i%10 != 0) {
				c++;
			}
			if(i/10 >=10 && i/10%10 == 0 && i%10 == 0) {
				c++;
			}
			}
		System.out.println(c);
	}
}

/**************************************************************
	Problem: 1750
	User: admin
	Language: Java
	Result: Accepted
	Time:844 ms
	Memory:40012 kb
****************************************************************/