UVA - 10669 - Three powers

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[] vals=new BigInteger[91];
        vals[0]=BigInteger.ONE;
        for(int i=1;i<91;i++){
            vals[i]=vals[i-1].multiply(BigInteger.valueOf(3));
        }
        while (true){
            BigInteger val=new BigInteger(br.readLine());
            if(val.compareTo(BigInteger.ZERO)==0)
                break;
            sb.append("{");
            val=val.subtract(BigInteger.ONE);
            int index=0;
            boolean first=true;
            for(;val.compareTo(BigInteger.ZERO)>0;val=val.divide(BigInteger.valueOf(2)),index++){
                if(val.mod(BigInteger.valueOf(2)).compareTo(BigInteger.ONE)==0){
                    if(!first)
                        sb.append(",");
                    first=false;
                    sb.append(" ").append(vals[index]);
                }
            }
            sb.append(" }\n");
        }
        System.out.print(sb);
    }
}