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



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