import java.util.Scanner;
import java.util.HashMap;
public class Main {

    public static void main(String[] args) {
        Scanner Ent = new Scanner(System.in);
        String palabra = Ent.next();
        HashMap tablaHash = new HashMap();
        char arreglo[] =palabra.toCharArray();
        for (int i = 0; i < arreglo.length; i++) {
            if(!tablaHash.containsKey(arreglo[i])){
                tablaHash.put(arreglo[i], arreglo[i]);
            }
        }
        if(tablaHash.size() == 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