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();
		boolean check = true;
		for(int i=0;i<s.length();i++) {
			if(!(s.charAt(i)==t.charAt(i))) {
				check = false;
				break;
			}
		}
		if(check && t.length()==s.length()+1) {
			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();
		boolean check = true;
		for(int i=0;i<s.length();i++) {
			if(!(s.charAt(i)==t.charAt(i))) {
				check = false;
				break;
			}
		}
		if(check && t.length()==s.length()+1) {
			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();
		boolean check = true;
		for(int i=0;i<s.length();i++) {
			if(!(s.charAt(i)==t.charAt(i))) {
				check = false;
				break;
			}
		}
		if(check && t.length()==s.length()+1) {
			System.out.println("Yes");
		}
		else {
			System.out.println("No");
		}
	} main {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		String t = sc.next();
		boolean check = true;
		for(int i=0;i<s.length();i++) {
			if(!(s.charAt(i)==t.charAt(i))) {
				check = false;
				break;
			}
		}
		if(check && t.length()==s.length()+1) {
			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 boolean check = true; check true for(int i=0;i<s.length();i++) {
			if(!(s.charAt(i)==t.charAt(i))) {
				check = false;
				break;
			}
		} int i=0; int i=0; i 0 i<s.length() i s.length() s.length s i++ i++ i {
			if(!(s.charAt(i)==t.charAt(i))) {
				check = false;
				break;
			}
		} {
			if(!(s.charAt(i)==t.charAt(i))) {
				check = false;
				break;
			}
		} if(!(s.charAt(i)==t.charAt(i))) {
				check = false;
				break;
			} !(s.charAt(i)==t.charAt(i)) (s.charAt(i)==t.charAt(i)) s.charAt(i) s.charAt s i t.charAt(i) t.charAt t i {
				check = false;
				break;
			} check = false check false break; if(check && t.length()==s.length()+1) {
			System.out.println("Yes");
		}
		else {
			System.out.println("No");
		} check && t.length()==s.length()+1 check t.length()==s.length()+1 t.length() t.length t s.length()+1 s.length() s.length s 1 {
			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();
		boolean check = true;
		for(int i=0;i<s.length();i++) {
			if(!(s.charAt(i)==t.charAt(i))) {
				check = false;
				break;
			}
		}
		if(check && t.length()==s.length()+1) {
			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();
		boolean check = true;
		for(int i=0;i<s.length();i++) {
			if(!(s.charAt(i)==t.charAt(i))) {
				check = false;
				break;
			}
		}
		if(check && t.length()==s.length()+1) {
			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();
		boolean check = true;
		for(int i=0;i<s.length();i++) {
			if(!(s.charAt(i)==t.charAt(i))) {
				check = false;
				break;
			}
		}
		if(check && t.length()==s.length()+1) {
			System.out.println("Yes");
		}
		else {
			System.out.println("No");
		}
	}
}