import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		char[] alphabet = new char[26];
		for (int i = 0; i < s.length(); i++) {
			alphabet[s.charAt(i)-'A']++;
		}		
		boolean flag = false;
		for (int i = 0; i < alphabet.length; i++) {
			if(alphabet[i] == 1) {
				flag = true;
			}else if(alphabet[i] == 4) {
				flag = true;
			}
		}
		System.out.println((flag)?"No":"Yes");
	}

}

/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