import java.util.Scanner;

public class Main {
	public static void main(String[] args) {

		Scanner input = new Scanner(System.in);

		String S = input.next();
		String T = input.next();

		input.close();

		if(S.length() + 1 == T.length() & T.startsWith(S)) {

			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