/******************************************************************************
* This is a simple program to calculate the value of the nth Fibonacci        *
* number.  It is done using recursion, because everyone grew to love          *
* recursion in CS 130/134 :)                                                  *
*                                                                             *
* There are two errors in the program.                                        *
*   - The first is a compile time error which requires a very small change.   *
*   - The second is a semantic error which causes the program to crash.       *
*                                                                             *
* Your job is to play detective and fix the two errors.                       *
******************************************************************************/

import java.io.*;

public class fact {
    /**************************************************************************
    * The Fibonacci function will return the num'th Fibonacci number          *
    * F(0) = 0, F(1) = 1, F(n) = F(n-1) + F(n-2)                              *
    * PRE: num >= 0                                                           *
    * POST: result = F(num)                                                   *
    **************************************************************************/
    public static int fibonacci (int num) {
	int calc = 0;  // The value of num! to be returned

	if (num <= 1)  // F(0) = 0, F(1) = 1, assume num >= 0
	    calc = num;
	else           // num > 1
	    calc = fibonacci (num - 1) + fibonacci (num);

	return calc;
    }

    /**************************************************************************
    * The main routine                                                        *
    **************************************************************************/
    public static void main (String [] args) {
	int number = 0;       // The number read in

	// See if we have the correct number of input parameters
	if (args.length != 1) {
	    System.out.println ("You must provide a paramater of 1 number.");
	    System.exit (-1);
	}

	// Try to convert the parameter to a number
	try {
	    number = Integer.parseInt (args [0]);
	} catch (NumberFormatException x) {
	    System.out.println ("The parameter must be a number.");
	    System.exit (-1);
	}

	// Check that it is at least 0
	if (number < 0) {
	    System.out.println
	     ("Can only calculate non-negative Fibonacci number.");
	    System.exit (-1);
	}

	// Calculate the result
	System.out.println (fibonacci (number));
    }

    private fib () {}
}