public class Fibonacci {
     

     // ------------------------------------------------------------------------------
     // Fibonacci function, "the rabbit counting function"
     
     public static int fib (int n) {
          if (n <= 1) {
               return n;
          } else {
               return fib(n-1) + fib(n-2);
          }
     }
     
     public static int fibIter (int n) {
          if (n == 0) {
               return 0;
          } else {
               return fibTail(n,1,0,1);
          }
     }
     
     public static int fibTail (int n, int i, int FibIMinus1, int FibI) {
          if (n == i) {
               return FibI;
          } else {
               return fibTail(n, i+1, FibI, FibIMinus1 + FibI);
          }
     }
     
     public static void main(String [] args) {
          if (args.length != 2) {
               System.out.println("Usage:  java Fib fib n");
               System.exit(-1);
          }
          int n = Integer.parseInt(args[1]);
          if (args[0].equals("fib"))
               System.out.println("fib(" + n + ") => " + fib(n));
          else if (args[0].equals("fibIter"))
               System.out.println("fibIter(" + n + ") => " + fibIter(n));

           else
               System.out.println("Unrecogized fibonacci version: " + args[0]);
     }
     
      
 }