import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		Set set = new HashSet<>();
		char s[] = sc.next().toCharArray();
		for (int i=0; i<s.length; i++) {
			set.add(s[i]);
		}

		System.out.println(set.size()==2 ? "Yes" : "No");

//		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