You are a chemist. Now you are given a product molecule. Please predict the the reactant molecules of the reaction.
The reaction equation has the following format:
```
reactant1.reactant2. ... .reactantN>>product
```
Your task is to predict the structure representation of the reactant molecule. We provide the SMILES of the reactants.
system
Do retrosynthesis with the product <molecule_2d> .
user
OK. The reactants may be CCNC(=O)Nc1nc2cc(-c3cnc(N4CCC(C)(C(=O)OCC)CC4)nc3)cc(C(=O)NCC)c2s1 .
assistant