Be very careful as almost all Hak Ip seeds are a form of "chicken tongue", or abortive, seeds and most likely will not be viable. In addition, the viable seeds have a very short viability period, approximately a week or so.
In addition, unless you are in for growing a tree with a 10 year or so (possibly up to 20 years or so) wait to see how it turns out, growing a lychee seed may be more of a waste of space and time. Grafting is not a recommended form of propagation; most lychee trees are air layered.