import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        List<String> array = new ArrayList<>();
        array.add(String.valueOf(s.charAt(0)));
        array.add(String.valueOf(s.charAt(1)));
        array.add(String.valueOf(s.charAt(2)));
        array.add(String.valueOf(s.charAt(3)));
        Collections.sort(array);
        if (array.get(0).equals(array.get(1)) && !array.get(1).equals(array.get(2)) && array.get(2).equals(array.get(3))) {
            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