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:
The role of extranuclear signaling actions of progesterone receptor in mediating progesterone regulation of gene expression and the cell cycle.

Ex Output:
progesterone


Ex Input:
Retigabine, a novel anti-convulsant, enhances activation of KCNQ2/Q3 potassium channels.

Ex Output:
potassium


Ex Input:
Breast cancer and steroid metabolizing enzymes: the role of progestogens.

Ex Output:

steroid