Democratic presidential hopeful Andrew Yang took to the stage at Tuesday night’s debate with an unusual lapel pin.

It said simply, “MATH.”

Yang has worn the pin for various media appearances before, and even sells it on his website to raise campaign funds.

“We need to do the opposite of much of what we’re doing right now, and the opposite of Donald Trump is an Asian man who likes math,” Yang cracked at the debate in July.

But while he does love math and is fond of breaking out numbers at his events, the pin also stands for something else: “Make America Think Harder.”

On Twitter, the “MATH” pin got more attention than some of the comments by the candidates: