import java.util.Scanner;
/*
    =====================================================
                   chapter 4: Loops

      Ex4: ID number check Digit valid
    =====================================================
*/

public class MyProgram {
    public static void main(String[] args) {
        
        //variables
        long id;
        long tmp;
        int checkDigit;
        int count=0;
        int sum=0,a;
        Scanner s=new Scanner(System.in);

        //user input
        System.out.println("Enter id number: ");
        id=s.nextLong();
        
        tmp=id/10;
        checkDigit= (int) (id%10);

        for(int i=0;i<8;i++)
        {
            if(i%2==0) {
                a = (int) ((tmp % 10) * 2);
                if(a<10)
                    sum += a;
                else
                    sum+= (a%10)+(a/10);
            }
            else
                sum+=(tmp%10);
            tmp/=10;

        }

        if((sum+checkDigit)%10==0)
            System.out.println("valid");
        else
            System.out.println("not");
    }
}