import java.util.*;
public class Main {
	public static void main(String[] args) {
    	Scanner sc = new Scanner(System.in);
		String S = sc.next();
		String T = sc.next();
		String ans = "Yes";
		
		if (S.length()+1!=T.length()) {
			ans = "No";	
		}
		if (S.equals(T.substring(0, T.length()-1))) {	
		}
		else{
		ans = "No";}
		System.out.println(ans);
		

    }
}
/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