 import java.util.*;
 public class Main{
	 public static void main(String arg[]){
		 Scanner sc=new Scanner(System.in);
		 String s=sc.next();
		 char ch[]=s.toCharArray();
		 Arrays.sort(ch);
		 if((ch[0]==ch[1])&&(ch[2]==ch[3])&&(ch[0]!=ch[2]))
			 System.out.println("Yes");
		 else System.out.println("No");
	 }
 }
/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