import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner scan = new Scanner(System.in);
        String testString = scan.next();
        Character one = testString.charAt(0);
        Character two = testString.charAt(1);
        Character three = testString.charAt(2);
        Character four = testString.charAt(3);
        if (one.equals(two) && three.equals(four) && !one.equals(three) && !one.equals(four)) {
            System.out.println("Yes");
        }
        else if (one.equals(three) && two.equals(four) && !one.equals(two) && !one.equals(four)) {
            System.out.println("Yes");
        }
        else if (one.equals(four) && two.equals(three) && !one.equals(two) && !one.equals(three)) {
            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