do {
        :
        :
        :
		:
        else
        {
            cout << "\nInvalid.";
            cout << "\nWould you like to calculate  your bill again ? (y / n) : ";
            cin >> ch;
            cout << endl;
        }
        

    }


    while (ch == 'Y' || ch == 'y');
    cout << "End of programm" <<endl;