import java.util.Scanner;
public class OctalToDecimal
{
    public static void main()
    {
        int count=0;
        Scanner sc=new Scanner(System.in);
        long octal=0,decimal=0,temp=0;
        boolean valid=true;
        System.out.print("ENTER OCTAL NUMBER:");
        octal=sc.nextInt();

        temp=octal;
        count=0;
        while(temp>0)
        {
            if(temp%10>7)
            {
                System.out.println("Invalid Octal Number");
                valid=false;
                break;
            }
            temp=temp/10;
        }
        if(valid==true)
        {
            temp=octal;
            while(temp>0)
            {
                decimal=decimal+(temp%10)*((long)Math.pow(8,count));
                count++;
                temp=temp/10;
            }
            System.out.println("THE DECIMAL VALUE OF OCTAL "+octal+" IS "+decimal);
        }

    }
}