C++ do while loop Gets inventory information from user

#include <iostream>
using namespace std;
#include <iomanip.h>
int main()/*from  w  w  w  .  j  a v  a  2  s  . c o  m*/
{
   int part_no, quantity;
   float cost, ext_cost;
   cout << "*** Inventory Computation ***\n\n";   // Title
   // Get inventory information.
   do
   {
      cout << "What is the next part number (-999 to end)? ";
      cin >> part_no;
      if (part_no != -999)
      {
         cout << "How many were bought? ";
         cin >> quantity;
         cout << "What is the unit price of this item? ";
         cin >> cost;
         ext_cost = cost * quantity;
         cout << "\n" << quantity << " of # " << part_no << " will cost " <<  setprecision(2) << ext_cost;
         cout << "\n\n\n";      // Print two blank lines.
      }
   } while (part_no != -999);       // Loop only if part  number is not -999.
   cout << "End of inventory computation\n";
   return 0;
}