//
// (Naively) Compute Fibonacci numbers.
//
// Warning: fibonacci(60) will take days to compute!
//
public class Fibonacci {
   public static long fib(long n) {
      if ( n <= 1 )
         return 1;
      else
         return fib(n -1 ) + fib(n - 2);
   }

   public static void main(String[] args) {
      if ( args.length != 1 )
         throw new IllegalArgumentException("Usage: java Fibonacci number");
      long number;
      try {
         number = Long.parseLong(args[0]);
      } catch ( NumberFormatException e ) {
         throw new IllegalArgumentException("Usage: java Fibonacci number\n  " + args[0]
                                            + " is not a number.");
      }
      long result = fib(number);
      java.text.NumberFormat withCommas = java.text.NumberFormat.getInstance();
      withCommas.setGroupingUsed(true);
      System.out.println("Fib of " + number + " is " 
                         + withCommas.format(result)); 
   }
}