import java.util.Scanner;
public class Main{
 public static void main(String[] args){
   Scanner sc = new Scanner(System.in);
   String S = sc.next();
   if(S.charAt(0)==S.charAt(1)&&S.charAt(1)==S.charAt(2)&&S.charAt(2)==S.charAt(3)){
     System.out.println("No");
   }else if(S.charAt(0)==S.charAt(1)){
     if(S.charAt(2)==S.charAt(3)){
     System.out.println("Yes");
     }else{
     System.out.println("No");
     }
   }else if(S.charAt(0)==S.charAt(2)){
     if(S.charAt(1)==S.charAt(3)){
     System.out.println("Yes");
     }else{
     System.out.println("No");
     }
   }else if(S.charAt(0)==S.charAt(3)){
     if(S.charAt(1)==S.charAt(2)){
     System.out.println("Yes");
     }else{
     System.out.println("No");
     }
   }else if(S.charAt(1)==S.charAt(2)){
     if(S.charAt(0)==S.charAt(3)){
     System.out.println("Yes");
     }else{
     System.out.println("No");
     }
   }else if(S.charAt(1)==S.charAt(3)){
     if(S.charAt(0)==S.charAt(2)){
     System.out.println("Yes");
     }else{
     System.out.println("No");
     }
   }else if(S.charAt(2)==S.charAt(3)){
     if(S.charAt(0)==S.charAt(1)){
     System.out.println("Yes");
     }else{
     System.out.println("No");
     }
   }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