Adding Edges

There are N+1 points on the plane, number A,1,2…N. N is an odd integer. Initially, there exist (N+1)/2 edges, as shown in the picture below.

Now your mission is add some edges to the graph, makes that
① degree(i) != degree(j), (i != j, 1 <= i, j <= N).
② degree(1) as small as possible.
For example, when N = 3, there are two possible answers:

Each test case contains a single odd integer N(N<=10^6), indicating the number of points. The input is terminated by a set starting with N = 0.

For each test case, output on a line the smallest possible value of the degree(1).

3
0

2

HDU 2009-4 Programming Contest