In this task, you are given a sentence. You are expected to recognize the name of any form of chemical substances. Although there might be several correct answers, you need to write one of them.

Ex Input:
Environmental pesticide exposure modulates cytokines, arginase and ornithine decarboxylase expression in human placenta.

Ex Output:
ornithine


Ex Input:
Management of psoriasis: the position of retinoid drugs.

Ex Output:
retinoid


Ex Input:
Potential diagnostic applications of side chain oxysterols analysis in plasma and cerebrospinal fluid.

Ex Output:

oxysterols