import java.util.*;

class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    String a = sc.nextLine();
    String b = sc.nextLine();
    if (a.equals(b.substring(0,a.length())) && a.length() +1 == b.length()){
      System.out.println("Yes");
    }
    else{
      System.out.println("No");
    }
  }

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

} Main public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    String a = sc.nextLine();
    String b = sc.nextLine();
    if (a.equals(b.substring(0,a.length())) && a.length() +1 == b.length()){
      System.out.println("Yes");
    }
    else{
      System.out.println("No");
    }
  } main {
    Scanner sc = new Scanner(System.in);
    String a = sc.nextLine();
    String b = sc.nextLine();
    if (a.equals(b.substring(0,a.length())) && a.length() +1 == b.length()){
      System.out.println("Yes");
    }
    else{
      System.out.println("No");
    }
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String a = sc.nextLine(); a sc.nextLine() sc.nextLine sc String b = sc.nextLine(); b sc.nextLine() sc.nextLine sc if (a.equals(b.substring(0,a.length())) && a.length() +1 == b.length()){
      System.out.println("Yes");
    }
    else{
      System.out.println("No");
    } a.equals(b.substring(0,a.length())) && a.length() +1 == b.length() a.equals(b.substring(0,a.length())) a.equals a b.substring(0,a.length()) b.substring b 0 a.length() a.length a a.length() +1 == b.length() a.length() +1 a.length() a.length a 1 b.length() b.length b {
      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
import java.util.*;

class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    String a = sc.nextLine();
    String b = sc.nextLine();
    if (a.equals(b.substring(0,a.length())) && a.length() +1 == b.length()){
      System.out.println("Yes");
    }
    else{
      System.out.println("No");
    }
  }

}