
import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
      String[] nyu=sc.nextLine().split("");
//     String nyu=sc.nextLine();

HashSet<String> list=new HashSet<>();

for(String temp:nyu)
list.add(temp);

if(list.size()!=2){
System.out.println("No");

}else{
int count=0;
for(int i=0;i<4;i++){
if(nyu[0].equals(nyu[i]))count++;
}

if(count==2){
System.out.println("Yes");

}else{
System.out.println("No");

}
}

//int num=Integer.parseInt(nyu);
//int numnext=Integer.parseInt(nyu[1]);
//int numend=Integer.parseInt(nyu[2]);

//System.out.println(numend);

//System.out.println(a/b);


	}
}
/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