How do I sum up every 5th number instead of all numbers?

Question

I need some help with the for-loop. I'm trying to sum up every fifth number that I type in, instead it sums them all up. What do I have to change?

        int count = 0;
        double total = 0;

        Console.Write("Enter your number: ");
        int input = int.Parse(Console.ReadLine());

        while (input != 0)
        {
            count++;
            for (count = 0; count <= 0; count += 5)
            {
                total = total + input;
            }
            Console.Write("Enter your number: ");
            input = int.Parse(Console.ReadLine());
        }
        Console.WriteLine("The sum of every +5 numbers is: {0}", total);
        Console.ReadKey();

Answer 1

Assuming that you enter a list of numbers, and the 1st number and every five afterwards is added (so 1st, 6th, 11th, etc.):

int count = 0;
double total = 0;

Console.Write("Enter your number: ");
int input = int.Parse(Console.ReadLine());

while (input != 0)
{
    count++;
    if (count % 5 == 1)
        total = total + input;
    Console.Write("Enter your number: ");
    input = int.Parse(Console.ReadLine());
}
Console.WriteLine("The sum of every +5 numbers is: {0}", total);
Console.ReadKey();

This works by using the modulo operator (%). The modulo operator returns the remainder of a division operation involving the number you specify.

In the code if (count % 5 == 1), the question is:

Is the remainder of count divided by 5 equal to 1?

If so, it adds the number. If not, it is skipped

The reason the remainder is one is because we want results 1, 6, 11, etc:

1 / 5 = remainder 1
6 / 5 = remainder 1
11 / 5 = remainder 1

If you change the modulo value to 0 it will return the results at position 5, 10, 15, etc.