UVA - 10334 - Ray Through Glasses

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("");
        String m="";
      
        BigInteger []arr=new BigInteger[5001];
        arr[0]=BigInteger.ONE;
        arr[1]=BigInteger.valueOf(2);
        for(int i=2;i<5001;i++){
            arr[i]=arr[i-1].add(arr[i-2]);
        }
        while((m=br.readLine())!=null){
            int x=Integer.parseInt(m);
            sb.append(arr[x]).append("\n");
        }
        System.out.print(sb);
    }
 
}