import java.util.*; 
 
class Main{
public static void main(String[] args){
	Scanner sc=new Scanner(System.in);
       
		String s=sc.next();
       
		String[] s1=s.split("");
    	
 	if(s1[0].equals(s1[1])&&s1[2].equals(s1[3])&&!(s1[0].equals(s1[2]))){
    		System.out.println("Yes");
    	}else if(s1[0].equals(s1[3])&&s1[2].equals(s1[1])&&!(s1[0].equals(s1[2]))){
     		System.out.println("Yes");
   	 }else if(s1[0].equals(s1[2])&&s1[1].equals(s1[3])&&!(s1[0].equals(s1[1]))){
    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