import java.util.Scanner;

public class Main{

		public static void main(String[] args) {
	        Scanner sc = new Scanner(System.in);
	        String str1 = sc.next();
	        String str2 = sc.next();
	        
	        if(str2.length() == str1.length()+1) {
	        String sub = str2.substring(0,str1.length());
	        if(sub.equals(str1)) {
	        	System.out.println("Yes"); 
	        }
	        else {
	        	System.out.println("No"); 
	        }
	        }
            
            

          
	        
            //System.out.println(res); 
	        
	}
}
/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