import java.util.Scanner;

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

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

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

} Main
import java.util.Scanner;

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

}