Can we define a norm such that the space of all sequences is a Hilbert space?

Question

Let $ \mathbb{K}^{\mathbb{N}} $ be the space of all complex sequence. How does one show that there exists no norm on $ \mathbb{K}^{\mathbb{N}} $ such that $ \mathbb{K}^{\mathbb{N}} $ is a Hilbert space. Unfortunately, I am quite lost in this question and don't even know where to start, so any clues would be much appreciated!

Thanks in advance!