import java.util.*;

public class No491{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);

		long N = sc.nextLong();
		long tmp = (long)Math.pow(10, 9) + 1;
		if(N < tmp) System.out.println(0);
		else{
			long div = N/tmp;
			long ans = 0;
			for(int i = 1; i <= div; i++){
				if(is_symmetry(i)) ans++;
			}
			System.out.println(ans);
		}
	}
	private static boolean is_symmetry(int n){
		String s = String.valueOf(n);
		int l = s.length();
		for(int i = 0; i < l/2; i++){
			if(s.charAt(i) != s.charAt(l-1-i)) return false;
		}
		return true;
	}
}