UVA - 10579 - Fibonacci Numbers

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigInteger;

public class Main {

    public static void main(String[] args) throws IOException {
        InputStreamReader isr = new InputStreamReader(System.in);
        BufferedReader br = new BufferedReader(isr);
        StringBuffer sb = new StringBuffer("");
        BigInteger[] bg=new BigInteger[5000];
        bg[0]=BigInteger.ZERO;
        bg[1]=BigInteger.ONE;
        int index=1;
        do{
            index++;
            bg[index]=bg[index-2].add(bg[index-1]);
        }while(bg[index].toString().length()<1001);
        String m="";
        while ((m=br.readLine())!=null) {
            int temp = Integer.parseInt(m);
            sb.append(bg[temp]).append("\n");
        }
        System.out.print(sb);
    }
}