import java.util.*;

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 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() - s.length() t.length() t.length t 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
import java.util.*;

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");
    }
  }
}