import java.util.Scanner;

class Main{
    public static void main(String args[]){
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();

        if(s.length() + 1 == t.length() && s.length() >= 1 && s.length() <= 10 && t.substring(0, t.length()-1).equals(s) == true){
            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