import 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();

        if (S.substring(0, S.length()).equals(T.substring(0, S.length()))
                && S.length() == T.length() - 1) {

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

        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