import java.util.*;
import java.io.*;
public class Main
{
	public static void main(String[] args) throws Exception{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String s = br.readLine().trim();
		String t = br.readLine().trim();
		if(s.equals(t.substring(0, t.length()-1))){
		    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