import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
    
		// 文字列の入力
       List<String> list = Arrays.asList(sc.next().split(""));
       Collections.sort(list);
    
		// 出力
		System.out.println(list.get(0).equals(list.get(1))
       && list.get(2).equals(list.get(3)) && !list.get(1).equals(list.get(2)) ? "Yes" : "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