Y by
In
of the vertices of the regular polygon
we write the number
and in the remaining ones we write the number
Let
be the number written on the vertex
A vertex is good if
for any integers
and
such that
Note that the indices are taken modulo
Determine the greatest possible value of
such that, regardless of numbering, there always exists a good vertex.






![\[x_i+x_{i+1}+\cdots+x_j>0\quad\text{and}\quad x_i+x_{i-1}+\cdots+x_k>0,\]](http://latex.artofproblemsolving.com/b/f/4/bf4cf984af7f310c1eb90b6b37126bfca9181305.png)




