import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int g = n % 10;
		int s = n / 10;
		if(g > s){
			System.out.println(g);
		}else if(g < s){
			System.out.println(s);
		}
	}

}
/**************************************************************
	Problem: 1622
	User: admin
	Language: Java
	Result: Accepted
	Time:608 ms
	Memory:40252 kb
****************************************************************/