import java.util.Scanner;
public class Main{
  public static void main(String[] args){
    Scanner sc=new Scanner(System.in);
    String str1=sc.nextLine();
    String str2=sc.nextLine();
    int m=str1.length();
    int n=str2.length();
    String new_str2=str2.substring(0,m);
    if(str1.equals(new_str2)){
      if(n==m+1){
          System.out.println("Yes");
      }else{
        System.out.println("No");
      }
    }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