UVA Problem ID 389 (Basically Speaking)

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
 {
  BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
  String input;
  StringBuilder sb=new StringBuilder(1000);
  
  while((input=br.readLine())!=null)
  {
   String numbers[]=input.trim().split(" +");
   BigInteger no=new BigInteger(numbers[0],Integer.parseInt(numbers[1]));
   String ans=no.toString(Integer.parseInt(numbers[2]));
   if(ans.length()>7)
    sb.append("  ERROR\n");
   else
   {
    while(ans.length()!=7)
     ans=" "+ans;
    sb.append(ans.toUpperCase()+"\n");
   }   
  }
  System.out.print(sb);
 }
}