Originally Posted by

**Dinkydoe** Hey, I'm a little stuck on the following problem:

Let $\displaystyle x_1,\cdots x_{kl+1}$ be n different real numbers. Show there exists a decreasing subsequence with at least k+1 terms, or a increasing sequence of at least l+1 terms. With as hint: $\displaystyle \chi(K_{lk+1})>lk$

Wich suggests that the result can be proven by seeing the numbers $\displaystyle x_i$ as vertices in the graph $\displaystyle K_{lk+1}$. Why this helps...I don't quite see this, yet.

Any suggestions?