import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner scan=new Scanner(System.in);
		String S=scan.next();
		char[] y=S.toCharArray();
		if(y[0]==y[1] && y[1]!=y[2] && y[2]==y[3])
		{
			System.out.println("Yes");
		}
		else if(y[0]==y[2] && y[2]!=y[1] && y[1]==y[3])
		{
			System.out.println("Yes");
		}
		else if(y[0]==y[3] && y[3]!=y[1] && y[1]==y[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