import java.util.*;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		String ans[] = { "Yes", "No" };
		int an = 0;
		sc.close();
		char tmp[] = s.toCharArray();
		Arrays.sort(tmp);
		int cnt = 1;
		if(tmp[0] != tmp[1] || tmp[2] != tmp[3])an = 1;
		if(tmp[0] == tmp[2])an = 1;
		System.out.println(ans[an]);
	}
}

/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