import java.io.*;
import java.util.Arrays;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
        String[] word = input.readLine().trim().split("");
        Arrays.sort(word);
        System.out.println(!(word[1].equals(word[2])) && word[0].equals(word[1]) && word[2].equals(word[3]) ? "Yes" : "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