import java.util.*;

public class Main{
	public static void main(String args[]) {

		Scanner sc = new Scanner(System.in);
		String S = sc.next();
		HashMap<Character, Integer> hm = new HashMap<>();
		char ch=' ';
		for(int i = 0; i < 4; i++) {
			ch = S.charAt(i);
			if(!hm.containsKey(ch)) {
				hm.put(ch, 1);
			}
			else {
				hm.put(ch, hm.get(ch) + 1);
			}
		}
		System.out.println((hm.size() == 2 && hm.get(ch) == 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