import java.util.*;

class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    String a = sc.nextLine();
    String b = sc.nextLine();
    if (a.equals(b.substring(0,a.length())) && a.length() +1 == b.length()){
      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