The '~' symbol represents negated, in other words NOT

Show how you would realize the logic function

Z = ~A~BC~D

using only 2-input NAND gates. Draw a circuit diagram to show your implementation.

Where I'm stuck is, I'm trying to figure out if I'm supposed to use laws to simplify this logic equation or just make a diagram out of it.

Here is my diagram of the question: http://imgur.com/8z3JaB5

I know this diagram is wrong but how am I supposed to only use 2 NAND gates when it is (AB) (CD) that means there is 3 gates

Thanks in advance, any help will be appreciated.