// This program gives Lucas numbers.

import java.util.Scanner;

public class Lucas
{
    public static void main ( String args [])
    {
        int input = -1;

        Scanner i = new Scanner ( System.in );

        while (input <0 || input >76)
        {
            System.out.print("Which Lucas number would you like? ");
            input = i.nextInt();
        }

        System.out.printf("Lucas #%d is %.0f\n", input, getLucas(input));

    }

    /**
      * This method gets user input to calculate Lucas numbers
      * 
      * @param input    The desired lucas number requested by user
      * @return         The calculated lucas number as a double
      */
    public static double getLucas( int input )
    {
        double lucas;
        double num1 = 2;
        double num2 = 1;
        double num3 = 0;
        int count = 0;

        if (input == 0)
            lucas = 2;
        else if (input == 1)
            lucas = 1;
        else
        {
            while ( count < input-1 )
            {
                num3 = num1 + num2;
                num1 = num2;
                num2 = num3;

                count++;
            }
            lucas = num3;
        }

        return lucas;
    }
}