import java.util.*;

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

    Arrays.sort(c); 	    

    if(c[0]==c[1] && c[2]==c[3] && c[0]!=c[3]){
 	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