(URI) Estiagem - Solução

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;

class Main  {
    public static int sumX;
    public static int sumY;

    public static int reader(BufferedReader br) throws NumberFormatException, IOException {    
        int n;
        int resp = 0;        
     
        while (true) {        
            n = br.read();        
            if (n >= '0' && n <= '9') {
                break;
            }
        }
          
        while (true) {        
            resp = resp*10 + n-'0';        
            n = br.read();        
            if (n < '0' || n > '9') {
                break;    
            }
        }
     
        return resp;    
    }
  
    public static void readEntries(BufferedReader br, Consumption[] list, int n) throws NumberFormatException, IOException {
      for (int i = 0; i < n; i++) {
            int x = reader(br);
            int y = reader(br);
          
            sumX += x;
            sumY += y;

            Consumption c = new Consumption(x, y/x);
            list[i] = c;            
        }
    }
  
    public static int checkAverage(Consumption[] list, Consumption[] list2, int n) {
        int index = 0;
      
        for (int i = 0; i < n; i++) {
            boolean averageAdded = false;
            if (list[i].x != -1) {
                for (int j = i+1; j < n; j++) {
                    if (list[i].average != list[j].average) {
                        break;
                    }
                    else {
                        if (!averageAdded) {
                            Consumption c = new Consumption(list[i].x+list[j].x, list[i].average);
                            list2[index] = c;
                            averageAdded = true;
                        }
                        else {
                            Consumption c = new Consumption(list2[index].x+list[j].x, list2[index].average);
                            list2[index] = c;
                        }
                        Consumption tmp = new Consumption(-1, -1);
                        list[j] = tmp;
                    }
                }
                if (!averageAdded) { // if there was not any other slot equal do the current slot
                    Consumption c = new Consumption(list[i].x, list[i].average);
                    list2[index] = c;
                }
                index++;
            }
        }
      
        return index;
    }
  
    public static void printAnswer(Consumption[] list2, int length, int count) {
        System.out.println("Cidade# " + count + ":");
      
        for (int i = 0; i < length-1; i++) {
            System.out.print(list2[i].x + "-" + list2[i].average + " ");
        }
        System.out.println(list2[length-1].x + "-" + list2[length-1].average);
      
        DecimalFormat df = new DecimalFormat("#.00");
        df.setRoundingMode(RoundingMode.DOWN);
        System.out.println("Consumo medio: " + df.format((double)sumY/sumX) + " m3.");
    }
  
    public static void process() throws NumberFormatException, IOException {  
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      
        int count = 0;
      
        int n = reader(br);
        while (n != 0) {
            if (count > 0) {
                System.out.println();
            }
          
            sumX = 0;
            sumY = 0;
          
            Consumption[] list = new Consumption[n];
            readEntries(br, list, n);
          
            Arrays.sort(list);
          
            Consumption[] list2 = new Consumption[n];
            int length = checkAverage(list, list2, n);
          
            count++;
            printAnswer(list2, length, count);
          
            n = reader(br);
        }
              
        return;
    }
  
    public static void main(String[] args) throws NumberFormatException, IOException {
        Main m = new Main();
        m.process();

        System.exit(0);
    }
}

class Consumption implements Comparable<Consumption> {
    public int x;
    public int average;
  
    public Consumption(int x, int average) {
        this.x = x;
        this.average = average;
    }
  
    public int compareTo(Consumption compareCons) {
        int compare = compareCons.average;
      
        return this.average-compare;
    }
}