import java.util.Scanner;
public class Main {
	public static void main(String[] args) {
		Scanner sc =new Scanner(System.in);
		String S = sc.next();
		String[] SArray = S.split("");
		if(SArray[0].equals(SArray[1])&&SArray[0].equals(SArray[2])&&SArray[0].equals(SArray[3])) {
			System.out.println("No");
			}else if(SArray[0].equals(SArray[1])) {
			if(SArray[2].equals(SArray[3])){
				System.out.println("Yes");
			}else{
              System.out.println("No");
            }
		}else if(SArray[0].equals(SArray[2])) {
			if(SArray[1].equals(SArray[3])){
				System.out.println("Yes");
			}else{
              System.out.println("No");
            }
		}else if(SArray[0].equals(SArray[3])) {
			if(SArray[1].equals(SArray[2])) {
			System.out.println("Yes");
			}else{
              System.out.println("No");
            }
		}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