import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
        String S = sc.nextLine();
        String T = sc.nextLine();
		if(S.length() + 1 == T.length()) {
			
			String TS = T.substring(0,S.length());
			if(TS.equals (S)) {
				System.out.println("Yes");
			}else {
				System.out.println("No");
			}
			
		}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