#!/usr/bin/env perl
# Copyright 2005 Daniel Cer (daniel.cer@cs.colorado.edu)
#
# This work is licensed under the Creative Commons Attribution-NonCommercial-
# ShareAlike License. To view a copy of this license, visit 
# http://creativecommons.org/licenses/by-nc-sa/2.5/ or send a letter to 
# Creative Commons, 543 Howard Street, 5th Floor, San Francisco, California, 
# 94105, USA.

sub fibonacci ($) {
  my $n = shift; my ($fib, $prev_fib) = (1,1); my $i;
  return -1 if ($n <= 0);
  for ($i = 2; $i < $n; $i++) {
    ($fib, $prev_fib) = ($fib + $prev_fib, $fib);
  }
  return $fib;
}

if ($#ARGV != 0) {
  print stderr "Usage:\n\t$0 (n-th fibonacci # to calculate)\n";
  exit -1;
}

$n = $ARGV[0];
print "fibonacci($n): ".fibonacci($n)."\n";