import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String n1 = sc.nextLine();
		String n2 = sc.nextLine();
		if (n1.length() + 1 != n2.length()) {
			System.out.println("No");
		}else{
			String[] n1sp = n1.split("");
			String[] n2sp = n2.split("");
			int count = 0;
			for (int i = 0; i < n1.length(); i++) {
				if (!(n1sp[i].equals(n2sp[i]))){
				System.out.println("No");
				break;
				}else{
				count++;
				}
			}
			if(count == n1.length())
			System.out.println("Yes");
		}
    }
}
/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