import java.util.Scanner;

public class Main{

	public static void main(String[] args) {
		Scanner scn = new Scanner(System.in);
      	String s = scn.next();
      	String t = scn.next();
      	if(s.length() == t.length() - 1){
        	if(s.equals(t.substring(0, s.length()))){
            	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