poj 2413 How many Fibs?

import java.io.BufferedInputStream;
import java.math.BigInteger;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(new BufferedInputStream(System.in));
BigInteger big[] = new BigInteger[501];
big[1] = BigInteger.valueOf(1);
big[2] = BigInteger.valueOf(2);
for(int i=3; i<=500; i++)
big[i] = big[i-1].add(big[i-2]);
int i, ret;
BigInteger a, b;
while(true) {
a = in.nextBigInteger();
b = in.nextBigInteger();
if(a.compareTo(b) == 0 && a.compareTo(BigInteger.valueOf(0)) == 0)
break;
i = 1;
ret = 0;
while(big[i].compareTo(a) < 0)
i++;
while(big[i].compareTo(b) <= 0) {
ret++;
i++;
}
System.out.println(ret);
}
}
}