fibonacci series, iterative version, BigInteger in Java

import java.math.BigInteger;

/**
 * Created by iamcreasy on 6/15/2016.
 */
public class Test2 {
    public static void main(String[] args) {
        long currentTime = System.currentTimeMillis();

        System.out.println(fib(1000));

        System.out.println("\nfib function took " + (System.currentTimeMillis() - currentTime) + " miliseconds");
    }

    static BigInteger fib(long nth){
        nth = nth - 1;
        long count = 0;
        BigInteger first = BigInteger.ZERO;
        BigInteger second = BigInteger.ONE;

        BigInteger third = null;
        while(count < nth){
            third = new BigInteger(first.add(second).toString());
            first = new BigInteger(second.toString());
            second = new BigInteger(third.toString());
            count++;
        }

        return third;
    }
}

// Output :
// 4346655768693745643568852767504062580256466051737178040248172908953655541794905189040387984007925516929592259308032
// 2634775209689623239873322471161642996440906533187938298969649928516003704476137795166849228875
//
// fib function took 41 miliseconds