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 ss = s.substring(0, s.length());
        String ts = t.substring(0, s.length());

        if(ss.equals(ts) && s.length()+1 == t.length()){
            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();

        String ss = s.substring(0, s.length());
        String ts = t.substring(0, s.length());

        if(ss.equals(ts) && s.length()+1 == t.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();

        String ss = s.substring(0, s.length());
        String ts = t.substring(0, s.length());

        if(ss.equals(ts) && s.length()+1 == t.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();

        String ss = s.substring(0, s.length());
        String ts = t.substring(0, s.length());

        if(ss.equals(ts) && s.length()+1 == t.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 String ss = s.substring(0, s.length()); ss s.substring(0, s.length()) s.substring s 0 s.length() s.length s String ts = t.substring(0, s.length()); ts t.substring(0, s.length()) t.substring t 0 s.length() s.length s if(ss.equals(ts) && s.length()+1 == t.length()){
            System.out.println("Yes");
        }else{
            System.out.println("No");
        } ss.equals(ts) && s.length()+1 == t.length() ss.equals(ts) ss.equals ss ts s.length()+1 == t.length() s.length()+1 s.length() s.length s 1 t.length() t.length t {
            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();

        String ss = s.substring(0, s.length());
        String ts = t.substring(0, s.length());

        if(ss.equals(ts) && s.length()+1 == t.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();

        String ss = s.substring(0, s.length());
        String ts = t.substring(0, s.length());

        if(ss.equals(ts) && s.length()+1 == t.length()){
            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();

        String ss = s.substring(0, s.length());
        String ts = t.substring(0, s.length());

        if(ss.equals(ts) && s.length()+1 == t.length()){
            System.out.println("Yes");
        }else{
            System.out.println("No");
        }
    }
}
