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);
		

    }
} import java.util.*; util.* java 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);
		

    }
} 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);
		

    } main {
    	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);
		

    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String S = sc.next(); S sc.next() sc.next sc String T = sc.next(); T sc.next() sc.next sc String ans = "Yes"; ans "Yes" if (S.length()+1!=T.length()) {
			ans = "No";	
		} S.length()+1!=T.length() S.length()+1 S.length() S.length S 1 T.length() T.length T {
			ans = "No";	
		} ans = "No" ans "No" if (S.equals(T.substring(0, T.length()-1))) {	
		}
		else{
		ans = "No";} S.equals(T.substring(0, T.length()-1)) S.equals S T.substring(0, T.length()-1) T.substring T 0 T.length()-1 T.length() T.length T 1 {	
		} {
		ans = "No";} ans = "No" ans "No" System.out.println(ans) System.out.println System.out System System.out ans String[] args args 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);
		

    }
} 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);
		

    }
} Main
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);
		

    }
}