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();
      boolean flag = false;
	if(T.startsWith(S)){
      if(T.length() == (S.length() + 1))
        flag = true;
    }
  if(flag)
    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