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();
      	if(T.length() == S.length()+1 && T.indexOf(S) == 0){
          System.out.println("Yes");
        }
        else{
        System.out.println("No");
        }
    }
} 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();
      	if(T.length() == S.length()+1 && T.indexOf(S) == 0){
          System.out.println("Yes");
        }
        else{
        System.out.println("No");
        }
    }
} Main public static void main (String[] args){ 
		Scanner sc = new Scanner(System.in);
		String S = sc.next();
      	String T = sc.next();
      	if(T.length() == S.length()+1 && T.indexOf(S) == 0){
          System.out.println("Yes");
        }
        else{
        System.out.println("No");
        }
    } main { 
		Scanner sc = new Scanner(System.in);
		String S = sc.next();
      	String T = sc.next();
      	if(T.length() == S.length()+1 && T.indexOf(S) == 0){
          System.out.println("Yes");
        }
        else{
        System.out.println("No");
        }
    } 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 if(T.length() == S.length()+1 && T.indexOf(S) == 0){
          System.out.println("Yes");
        }
        else{
        System.out.println("No");
        } T.length() == S.length()+1 && T.indexOf(S) == 0 T.length() == S.length()+1 T.length() T.length T S.length()+1 S.length() S.length S 1 T.indexOf(S) == 0 T.indexOf(S) T.indexOf T S 0 {
          System.out.println("Yes");
        } System.out.println("Yes") System.out.println System.out System System.out "Yes" {
        System.out.println("No");
        } System.out.println("No") System.out.println System.out System System.out "No" 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();
      	if(T.length() == S.length()+1 && T.indexOf(S) == 0){
          System.out.println("Yes");
        }
        else{
        System.out.println("No");
        }
    }
} public class Main{
	public static void main (String[] args){ 
		Scanner sc = new Scanner(System.in);
		String S = sc.next();
      	String T = sc.next();
      	if(T.length() == S.length()+1 && T.indexOf(S) == 0){
          System.out.println("Yes");
        }
        else{
        System.out.println("No");
        }
    }
} 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();
      	if(T.length() == S.length()+1 && T.indexOf(S) == 0){
          System.out.println("Yes");
        }
        else{
        System.out.println("No");
        }
    }
}