import java.util.Scanner;
public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String N = sc.next();
		String[] str = N.split("");
		String s1, s2 = "";
		int cnt = 0;
		s1 = str[0];
		for (String a : str) {
			if (!((a.equals(s1) && !a.equals(s2)) || ((!a.equals(s1) && a.equals(s2))))) {
				cnt++;
			}
			if (!a.equals(s1) && s2.equals(""))
				s2 = a;
		}
	if(cnt==1)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