import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		String S = scan.next();
		String T = scan.next();

		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 scan = new Scanner(System.in);

		String S = scan.next();
		String T = scan.next();

		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 scan = new Scanner(System.in);

		String S = scan.next();
		String T = scan.next();

		if(T.length() == S.length() + 1 && S.equals(T.substring(0, S.length()))) {
			System.out.println("Yes");
		} else {
			System.out.println("No");
		}
	} main {

		Scanner scan = new Scanner(System.in);

		String S = scan.next();
		String T = scan.next();

		if(T.length() == S.length() + 1 && S.equals(T.substring(0, S.length()))) {
			System.out.println("Yes");
		} else {
			System.out.println("No");
		}
	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) String S = scan.next(); S scan.next() scan.next scan String T = scan.next(); T scan.next() scan.next scan 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() T.length T S.length() + 1 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 scan = new Scanner(System.in);

		String S = scan.next();
		String T = scan.next();

		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 scan = new Scanner(System.in);

		String S = scan.next();
		String T = scan.next();

		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 scan = new Scanner(System.in);

		String S = scan.next();
		String T = scan.next();

		if(T.length() == S.length() + 1 && S.equals(T.substring(0, S.length()))) {
			System.out.println("Yes");
		} else {
			System.out.println("No");
		}
	}
}