Hi Guys I really in trouble with a problem about dilwor theorem

The problem states:

Let $\displaystyle a_1 , a_2 , . . . , a_{

n^2 +1} $ be a permutation of the integers

$\displaystyle 1, 2, . . . , n^2 + 1 $. Show that Dilworth’s theorem implies that the

sequence has a subsequence of length $\displaystyle n + 1 $ that is monotone.

Thanks a lot to all of you

All the best

joksy