import java.io.BufferedInputStream;
import java.util.Scanner;

public class Main {
    private static Scanner sc = new Scanner(new BufferedInputStream(System.in));

    public static void main(String[] args) {
        String s1 = sc.nextLine();
        String s2 = sc.nextLine();
        if (s1.length() + 1 == s2.length() && s1.equals(s2.substring(0, s1.length()))) {
            System.out.println("Yes");
        }else{
            System.out.println("No");
        }
    }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz