If function - equal/different/blank

I'm trying to write an formula that will give me the following result: IF H1=H2, write "OK", if they are different, write "NO", if H1 is blank, then become blank too. I tried like this:

=IF(H1=H2;"OK";"NO";IF(H1="";""))

And it says I've entered too many arguments for this function.

Any advice?