import java.util.Scanner;
class Main{
  public static void main(String[] args){
    Scanner stdIn = new Scanner(System.in);
    
    String S = stdIn.next();
    String T = stdIn.next();
    
    int count = 0;
    for(int i = 0;i < S.length();i++){
      if(S.charAt(i) == T.charAt(i)){
        count++;
      }
      else
        break;
    }
    
    if(count == S.length() && S.length() + 1 == T.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