import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        String s = sc.next();
        String[] str = new String[4];
        str = s.split("");
        if (str[0].equals(str[1]) && str[2].equals(str[3]) && !str[1].equals(str[2]))
            System.out.println("Yes");
        else if (str[0].equals(str[2]) && str[1].equals(str[3]) && !str[1].equals(str[2]))
            System.out.println("Yes");
        else if (str[0].equals(str[3]) && str[1].equals(str[2]) && !str[1].equals(str[0]))
            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