import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        
        String a = sc.next().trim();
        String b = sc.next().trim();
        
        int len = b.length() - a.length();
        
        if (len == 1 && b.startsWith(a)) {
            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 a = sc.next().trim();
        String b = sc.next().trim();
        
        int len = b.length() - a.length();
        
        if (len == 1 && b.startsWith(a)) {
            System.out.println("Yes");
        } else {
            System.out.println("No");
        }
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        
        String a = sc.next().trim();
        String b = sc.next().trim();
        
        int len = b.length() - a.length();
        
        if (len == 1 && b.startsWith(a)) {
            System.out.println("Yes");
        } else {
            System.out.println("No");
        }
    } main {
        Scanner sc = new Scanner(System.in);
        
        String a = sc.next().trim();
        String b = sc.next().trim();
        
        int len = b.length() - a.length();
        
        if (len == 1 && b.startsWith(a)) {
            System.out.println("Yes");
        } else {
            System.out.println("No");
        }
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String a = sc.next().trim(); a sc.next().trim() sc.next().trim sc.next() sc.next sc String b = sc.next().trim(); b sc.next().trim() sc.next().trim sc.next() sc.next sc int len = b.length() - a.length(); len b.length() - a.length() b.length() b.length b a.length() a.length a if (len == 1 && b.startsWith(a)) {
            System.out.println("Yes");
        } else {
            System.out.println("No");
        } len == 1 && b.startsWith(a) len == 1 len 1 b.startsWith(a) b.startsWith b a {
            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 a = sc.next().trim();
        String b = sc.next().trim();
        
        int len = b.length() - a.length();
        
        if (len == 1 && b.startsWith(a)) {
            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 a = sc.next().trim();
        String b = sc.next().trim();
        
        int len = b.length() - a.length();
        
        if (len == 1 && b.startsWith(a)) {
            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 a = sc.next().trim();
        String b = sc.next().trim();
        
        int len = b.length() - a.length();
        
        if (len == 1 && b.startsWith(a)) {
            System.out.println("Yes");
        } else {
            System.out.println("No");
        }
    }
}