const int SIZE = 6;

main()
{
    String filename;
    ifstream input;
    int num;
    double total = 0.0;
    int readings = 0;
    
    int a[SIZE];                       // track most recent readings
    for(num=0; num < SIZE; num++){
	a[num] = 0;
    }
    cout << "enter file name: ";
    cin >> filename;
    input.open(filename);

    int period = 0;
    while(input >> num){
	total -= a[period];              // subtract last reading
	a[period] = num;                 // store this reading
	total += num;                    // add this reading
	period++;
	readings++;
	
	if (period == SIZE){
	    period = 0;
	}
	if (readings >= SIZE){
	    cout << total << endl;
	}
    }
    input.close();
}

void
NoDupes(int a[], int & numElts)
//precondition: a is sorted: a[0] <= a[1] <= ... <= a[numElts - 1]     
//postcondition: duplicates in a removed, a still sorted
{
    int lastNonDup = 0;                  // location of last non-duplicate
    int k;

    for(k=1; k < numElts; k++){
        if (a[k] != a[lastNonDup]){

	    lastNonDup++;               // new non-dup, update position
            a[lastNonDup] = a[k];       // not a duplicate, store it

        }
    }
    numElts = lastNonDup + 1;          // potentially fewer elts, update
}

double CartWorth(const Grocery cart[], int numItems)
// precondition: numItems = # of grocery items in cart
// postcondition: returns total cost of all items in cart
{
    double total = 0.0;
    int k;
    for(k=0; k < numItems; k++){
	total += cart[k].price;
    }
    return total;
}

void ReadCart(Grocery cart[], int & numItems, istream & input)
// precondition: input open for reading
// postcondition: all entries in stream stored in cart,     
//                numItems = # items in cart
{
    String name,price,type;

    numItems = 0;
    
    while(name.GetLine(input,':') &&
	  price.GetLine(input,':') &&
	  type.GetLine(input)){

	cart[numItems].brandname = name;
	cart[numItems].price = atof(price);
	cart[numItems].type = StringToKind(type);
    }
}