import java.util.*;
public class Main {
  public static void main(String... args) {
   	Scanner input = new Scanner(System.in);
  	String first = input.next();
    String second = input.next();
    
    int n = first.length();
    
    if (second.length() != n + 1) {
      System.out.println("No");
      return;
    }
    
    if (!second.substring(0, n).equals(first)) {
      System.out.println("No");
      return;
    }
    
    System.out.println("Yes");
  }
}
/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