import java.util.Scanner;

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

		String s1 = s.replaceAll(s.substring(0,1), "");
		String s2;
		if(s1.length() != 0) {
			s2 = s1.replaceAll(s1.substring(0, 1), "");
		}else {
			s2 = "AAAAA";
		}
		
		if(s1.length() == 2 && s2.length() ==0) {
			System.out.println("Yes");
		}else {
			System.out.println("No");
		}
				
		sc.close();	
	}
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz