import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		String s = sc.nextLine();
		String t = sc.nextLine();

		sc.close();


		if (s.equals(t.substring(0, t.length()-1)) &&
				t.matches(s + "[a-z]")) {
				//t.substring(t.length(), t.length()).matches("[a-z]")) {
			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