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:
Transdermal selegiline for the treatment of major depressive disorder.

Ex Output:
selegiline


Ex Input:
Blockage of the HERG human cardiac K+ channel by the gastrointestinal prokinetic agent cisapride.

Ex Output:
K+


Ex Input:
Vitamin E deficiency impairs the somatostatinergic receptor-effector system and leads to phosphotyrosine phosphatase overactivation and cell death in the rat hippocampus.

Ex Output:

phosphotyrosine