import java.util.Scanner;

public class Main {

  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    String s = sc.next();
    String t = sc.next();
    int len_s = s.length();
    if(t.length() - s.length() == 1 && s.equals(t.substring(0, s.length()))){
      System.out.println("Yes");
    } else {
      System.out.println("No");
    }
  }
} import java.util.Scanner; Scanner 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();
    int len_s = s.length();
    if(t.length() - s.length() == 1 && s.equals(t.substring(0, s.length()))){
      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();
    int len_s = s.length();
    if(t.length() - s.length() == 1 && s.equals(t.substring(0, s.length()))){
      System.out.println("Yes");
    } else {
      System.out.println("No");
    }
  } main {
    Scanner sc = new Scanner(System.in);
    String s = sc.next();
    String t = sc.next();
    int len_s = s.length();
    if(t.length() - s.length() == 1 && s.equals(t.substring(0, s.length()))){
      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 int len_s = s.length(); len_s s.length() s.length s if(t.length() - s.length() == 1 && s.equals(t.substring(0, s.length()))){
      System.out.println("Yes");
    } else {
      System.out.println("No");
    } t.length() - s.length() == 1 && s.equals(t.substring(0, s.length())) t.length() - s.length() == 1 t.length() - s.length() t.length() t.length t s.length() s.length s 1 s.equals(t.substring(0, s.length())) s.equals s t.substring(0, s.length()) t.substring t 0 s.length() s.length s {
      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();
    int len_s = s.length();
    if(t.length() - s.length() == 1 && s.equals(t.substring(0, s.length()))){
      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();
    int len_s = s.length();
    if(t.length() - s.length() == 1 && s.equals(t.substring(0, s.length()))){
      System.out.println("Yes");
    } else {
      System.out.println("No");
    }
  }
} Main
import java.util.Scanner;

public class Main {

  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    String s = sc.next();
    String t = sc.next();
    int len_s = s.length();
    if(t.length() - s.length() == 1 && s.equals(t.substring(0, s.length()))){
      System.out.println("Yes");
    } else {
      System.out.println("No");
    }
  }
}