Elon Musk has sent an ultimatum to all Twitter staff—commit to an “extremely hardcore” approach to work or quit your job by Thursday.

“Going forward, to build a breakthrough Twitter 2.0 and succeed in an increasingly competitive world, we will need to be extremely hardcore. This will mean working long hours at high intensity. Only exceptional performance will constitute a passing grade,” Musk wrote in the all-staff email.

The email’s subject line was, “A Fork in the Road.”