import java.math.BigInteger;
import java.io.*;

/**
 * BigFib is a simple class for computing Fibonacci
 * numbers, using the Java multi-precision integer
 * class java.math.BigInteger.
 */
public class BigFib {
    BigInteger last;
    BigInteger next;
    int n;

    /**
     * Create a new BigFib object, initialized to 0 on
     * the Fibonnacci sequence.
     */
    public BigFib () {
	n = 0;
	last = new BigInteger("0");
	next = new BigInteger("1");
    }
 
    /**
     * Compute c more Fibonnacci numbers, returning the
     * last one.  Ideally, c should be even and >0.
     * If you want to print the numbers too, pass printTo
     * as non-null.
     */
    public BigInteger getFib(int c, PrintStream printTo) {
	BigInteger tmp;
	for( ; c > 0; c -= 2) {
	    last = last.add(next);  n++;
	    if (printTo != null) printTo.println(" " + n + "\t" + last);
	    next = next.add(last);  n++;
	    if (printTo != null) printTo.println(" " + n + "\t" + next);
	}
	if (c == 0) return next;
	else return last;
    }

    /**
     * Default limit for self-test.
     */
    public static final int defaultLimit = 100;

    /**
     * Self-test code, accepts an integer from the
     * command line, or uses the default limit.
     */
    public static void main(String args[]) {
	 BigInteger answer;

	 BigFib fib = new BigFib();
	 
	 System.out.println("\t\t      Fibonacci sequence!");
	 System.out.println("");
 
	 System.out.println();
	 int limit = 100;
	 if (args.length > 0) {
	     try { limit = Integer.parseInt(args[0]); }
	     catch (NumberFormatException nfe) { 
		 System.err.println("Bad number, using default " + limit);
	     }
	     if (limit < 1) {
		 limit = defaultLimit;
		 System.err.println("Limit too low, using default " + limit);
	     }
	 }

	 answer = fib.getFib(limit, System.out);
    }
}