How Many Fibs? - UVa 10183 大数加法

import java.math.BigInteger;
import java.util.Scanner;

public class Main 
{
	public static void main(String [] args)
	{
		Scanner scan=new Scanner(System.in);
		BigInteger f[]=new BigInteger[1010],L,R,ret;
		int i,j,k;
		f[0]=new BigInteger("0");
		f[1]=new BigInteger("1");
		f[2]=new BigInteger("2");
		for(i=3;i<=1000;i++)
		   f[i]=f[i-2].add(f[i-1]);
		String s;//=f[1000].toString();
		//System.out.println(s.length());
		while(true)
		{
			L=scan.nextBigInteger();
			R=scan.nextBigInteger();
			if(L.equals(f[0]) && R.equals(f[0]))
			  break;
			for(i=1;i<=1000;i++)
			{
				ret=f[i].subtract(L);
				s=ret.toString();
				if(s.charAt(0)!='-')
				  break;
			}
			for(j=i;j<=1000;j++)
			{
				ret=R.subtract(f[j]);
				s=ret.toString();
				if(s.charAt(0)=='-')
					break;
			}
			//System.out.println(i+" "+j);
			System.out.println(j-i);
		}
	}

}