import java.util.*;
class Main{
  public static void main(String[] args){
    Set<Character>set = new HashSet<>();
    Scanner sc = new Scanner(System.in);
    String s = sc.next();
    set.add(s.charAt(0));
    set.add(s.charAt(1));
    set.add(s.charAt(2));
    set.add(s.charAt(3));
    if(set.size()==2)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