import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String username = sc.next();
        if (username.length() < 8 || username.length() > 30) {
            System.out.println("Invalid");
            return;
        }
        if (!Character.isLetter(username.charAt(0))) {
            System.out.println("Invalid");
            return;
        }
        for (int i = 0; i < username.length(); i++) {
            char c = username.charAt(i);
            if (!Character.isLetterOrDigit(c) && c != '_') {
                System.out.println("Invalid");
                return;
            }
        }
        System.out.println("Valid");
    }
}