import java.util.Scanner;

public class Main {

  public static void main(String[] args) {

    Scanner sc = new Scanner(System.in);

    int[] alp = new int[26];
    String s = sc.next();
    int cnt = 0;

    for (int i = 0; i < 4; i++) {
      alp[s.charAt(i) - 'A']++;
    }

    for (int i = 0; i < 26; i++) {
      if (alp[i] == 0) {
        continue;
      } else if (alp[i] == 2) {
        cnt++;
      } else {
        System.out.println("No");
        return;
      }
    }

    if (cnt == 2) {
      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