import java.util.*;
public class Main{
	public static void main(String[] args){
    
      Scanner sc = new Scanner(System.in);
      
      String a = sc.next();
      String n = sc.next();
      
      if (n.startsWith(a) && n.length() == a.length() + 1) {
      	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