import java.util.*;
class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String str = sc.next();
        String s1 = str.replace(str.substring(0,1),"");
        if(s1.length() !=2) {
            System.out.println("No");
            return;
        }
        String s2 = s1.replace(s1.substring(0,1),"");
        if(s2.length()==0) 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