# Circle containing points

Find all such positive integers $n\geq2$ that there exists a set of n points on a plane, every one of which lies outside of some circle containing all the other points and having the center in one of these points.

Could you please help me? I don't even understand how am I supposed to create such a circle... As "every one of which lies outside of some circle", how, at the same time, the circle can contain "all the other points"?

-
If this is homework, you should add the "homework" tag. – Dimitrije Kostic Nov 28 '11 at 15:03
"and having the middle in one of them" dangles in your sentence. There's something in one of the points? – Dimitrije Kostic Nov 28 '11 at 15:06
What does "having the middle in one of them" mean? Does middle mean centre? To what kind of object does "them" refer? – André Nicolas Nov 28 '11 at 15:12
Sorry for the confusion, changed. – Tom Reilly Nov 28 '11 at 17:25
Could you respond on whether I decrypted the task correctly – user1708 Nov 29 '11 at 15:34

If you intepret it such: Find all n such that we can have n points $p_i$, and n circles $C_t$, such that if $j\neq k$, then $p_j$ is contained in $C_k$, and each $C_q$ has a point $p_q$ at its center.
Then for every even $2\leq n$, we can place the points at the corners of a regular n-gon.