import java.util.*;

public class Main {
	public static void main(String[] args) {
		char[] s = new Scanner(System.in).next().toCharArray();
		Arrays.sort(s);
		System.out.println(s[0] == s[1] && s[2] == s[3] && s[1] != s[2] ? "Yes" : "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