Fill a circle with spheres of a given radius

Hello. I have a circle of radius R and I want ti fill it with spheres of radius r. How can I do it? I achieved the circle but I don't know how to create the spheres inside at correct positions.
Here is an example of what I want to do:

EDIT: I found this web page where I can calculate the number of spheres of radius r that fits into a circle of radius R. But it doesn't say how to place them.

Thanks!

 

A very simple approximate algorithm would be:

1. Calculate the radius of the outermost ring of spheres: A = R - r
2. Calculate the circumference of that ring: C = 2Aπ
3. Use this to calculate a first approximation of the number of spheres in that ring: N = (int)(C / (2r))
4. Now calculate the actual length of a side of a polygon with N sides inscribed in a circle of radius A: s = 2Asin(π/N)
5. While N > 1 and s < 2r (which would mean the spheres would overlap when placed), subtract 1 from N and recalculate (return to step 4)
6. If N = 1, set A to 0 (place single sphere in centre, not offset to one side)
7. Now that you have N, place N spheres around a circle of radius A:

Code (CSharp):

1. for (int i = 0; i < N; ++i)
2. {
3.    // make a sphere, then:
4.    float angle = Mathf.Pi * 2f * i / N;
5.    sphere.transform.position = new Vector3( A*Mathf.Cos(angle), 0f, A * Mathf.Sin(angle));
6. }

8. Subtract 2r from A. If the new value of A >= 0, go back to step 4 and continue reducing and fitting N and adding new rings of spheres.

 

I will try and post the results. Thanks!