import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    	String befId = sc.next();
    	String aftId = sc.next();
    
     String modId = aftId.substring(0, aftId.length()-1);
   	/* modId.setLength(aftId.length()-1);*/
    
    if(befId.equals(modId)) {
      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