import java.util.Scanner;
 
 
	public class Main{
	  public static void main(String[] args) {
		  
		  Scanner scanner = new Scanner(System.in);
		  
		    String S = scanner.next();
	 		String T = scanner.next();
	 		
		  if (T.length() == S.length()+1 && T.indexOf(S) == 0) {
			  System.out.println("Yes");
		  }
		  else{
			  System.out.println("No");
		  }
		  scanner.close();
	}
}
/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