import java.util.Scanner;

public class Main{
	public static void main(String[] args){
		Scanner scan = new Scanner(System.in);
		String S = scan.nextLine();
		String T = scan.nextLine();

		int amt = S.length();
		String T_part = T.substring(0, amt);

		if(T_part.equals(S) && T.length() == (amt + 1)){
			System.out.println("Yes");
		}else{
			System.out.println("No");
		}

		scan.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