import java.util.*;

public class Main{
	public static void main(String args[]){
    	Scanner scan = new Scanner(System.in);
        String S = scan.next();
        String str[] = new String[S.length()];
        for( int i = 0 ; i < S.length() ; i++ ){
            str[i] = String.valueOf(S.charAt(i));
        }
        Arrays.sort(str);
        String bol = str[0].equals(str[1]) && !(str[1].equals(str[2])) && str[2].equals(str[3]) ? "Yes" : "No" ;
        System.out.println(bol);
	}
}
/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