import java.util.*;
class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    String S = sc.next();
    String S1 = S.substring(0,1);
    String S2 = S.substring(1,2);
    String S3 = S.substring(2,3);
    String S4 = S.substring(3,4);
    if (S1.equals(S2) && S3.equals(S4) && !(S1.equals(S3))){
      System.out.println("Yes");
    }else if(S1.equals(S3) && S2.equals(S4) && !(S1.equals(S2))){
      System.out.println("Yes");
    }else if(S1.equals(S4) && S2.equals(S3) && !(S1.equals(S2))){
      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