import java.util.*;
public class Main {
	public static void main(String[] args){
      Scanner sc = new Scanner(System.in);
      String S = sc.next();
      String T = sc.next();

      if (S.length() != T.length()-1){
        System.out.println("No");
      } else {
        if (S.equals(T.substring(0, T.length()-1))){
          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