UVA - 10473 - Simple Base Conversion

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {

    public static void main(String[] args) throws IOException{
        InputStreamReader isr=new InputStreamReader(System.in);
        BufferedReader br=new BufferedReader(isr);
        StringBuilder sb = new StringBuilder("");
        String m="";
        while(true) {
            m=br.readLine();
            if(m.charAt(0) =='0' && m.charAt(1) =='x'){
                m=m.substring(2);
                sb.append(Integer.parseInt(m, 16)).append("\n");
            }else{
                if(Integer.parseInt(m)<0){
                    break;
                }
                sb.append("0x").append(Integer.toHexString(Integer.parseInt(m)).toUpperCase()).append("\n");
            }
        }
        System.out.print(sb);
    }
}