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(T.length() == S.length()+1 && T.indexOf(S) == 0){
          System.out.println("Yes");
        }
        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