import java.io.*;

 import java.util.*;

 import java.math.*;

 class Main

 {

     public static void main(String[] args)

     {

         Scanner sc = new Scanner(System.in);

         int kase = 0;

         while (true)

         {

             int n = sc.nextInt();

             int f = sc.nextInt();

             if (n == 0 && f == 0)  break;

             kase++;

             BigInteger sum = BigInteger.valueOf(0);

             for (int i = 0; i < n; i++)

             {

                 BigInteger t = sc.nextBigInteger();

                 sum = sum.add(t);

             }

             BigInteger aver = sum.divide(BigInteger.valueOf(f));

             System.out.println("Bill #" + kase + " costs " + sum + ": each friend should pay " + aver);

             System.out.println();

         }

     }

 }