import java.util.Scanner; public class HackerrankJava0025 { private static final Scanner scan = new Scanner(System.in); public static void main(String[] args) { // Valid Username Regular Expression // https://www.hackerrank.com/challenges/valid-username-checker/problem?isFullScreen=true int n = Integer.parseInt(scan.nextLine()); while (n-- != 0) { String userName = scan.nextLine(); if (userName.matches(UsernameValidator.regularExpression)) { System.out.println("Valid"); } else { System.out.println("Invalid"); } } scan.close(); } } class UsernameValidator { public static final String regularExpression = "^[a-zA-Z][a-zA-Z0-9_]{7,29}"; }