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

public class Main {

    public static void main(String[] args) {
        List<Integer> l = new ArrayList<>();
        Scanner sc = new Scanner(System.in);
        String s = sc.nextLine();
        for (int i = 0; i < s.length(); i++) {
            int x = s.charAt(i);
            l.add(x);
        }
        Collections.sort(l);
        if (l.get(0) == l.get(1) && l.get(2) == l.get(3) && l.get(0) != l.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