import java.util.Scanner;
public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner in = new Scanner(System.in);
		String s = in.next();
		String t = in.next();
		String t2 = t.substring(0,t.length()-1);
		boolean ok = false;

		if(s.equals(t2)) {
			ok = true;
		}
		if(ok){
			if(t.length()-s.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