import java.util.Scanner;

public class Main {

    private static Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) {

        solve();
    }

    private static void solve() {

        String s1 = scanner.next();
        String s2 = scanner.next();


        System.out.println(s2.startsWith(s1) && s2.length() == s1.length() + 1 ? "Yes" : "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