import java.util.Scanner;

public class Main {

    //https://atcoder.jp/contests/abc132/tasks/abc132_a
    public static void main( String[] args ) {

        Scanner scanner = new Scanner(System.in);

        String str = scanner.next();

        int[] arr = new int[26];
        for (int i = 0; i < 4; i++) {
            arr[str.charAt(i) - 'A']++;
        }

        int type = 0;
        for (int i = 0; i < 26; i++) {

            if (arr[i] > 0 && arr[i] == 2) {
                type++;
            }
        }

        System.out.println(type == 2 ? "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