import java.util.ArrayList;
import java.util.Scanner;
public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String str = sc.next();
		char[] ch = str.toCharArray();
		ArrayList<Character> check = new ArrayList<>();
		
		for(int i = 0; i < 4; i++) {
			if(!check.contains(ch[i])) {
				check.add(ch[i]);
			}
		}
		if(check.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