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 (s.length() + 1 != t.length()) {
            System.out.println("No");
            return;
        }

        if (!s.equals(t.substring(0, s.length()))) {
            System.out.println("No");
            return;
        }

        System.out.println("Yes");
    }
}

/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