import java.util.Scanner;
public class Q2
{
    public static void main(String[] args){
    Scanner kb=new Scanner(System.in);
    while (true){
        System.out.print("Enter your phone number: ");
        String number=kb.next();
        if(number.equals("exit")){
            System.exit(0);
        }
    boolean valid=true;
    for(int i=0;i<number.length();i++){
        if(number.length()!=10) valid=false;
    }
    if (valid) System.out.println("It is valid");
    else System.out.println("It is invalid");
    }
  }
}