Duolingo CEO Luis von Ahn took to LinkedIn on Monday to deliver a direct message to the company’s 42 newly hired graduates: Be nice, take initiative, and remember that success doesn’t require sacrificing your well-being.

In his LinkedIn post, the 47-year-old Guatemalan-American billionaire outlined five career tips for new hires, with his first piece of advice being blunt: “Don’t be a jerk,” he wrote. “Duolingo has an allergic reaction to toxic behavior, and our culture quickly identifies and rejects it.”

The language-learning platform’s CEO emphasized that new employees should avoid coming in with “massive egos” or being duplicitous with colleagues. His comments come as workplace toxicity has emerged as a leading driver of employee turnover, with recent research from Revelio Labs shared by MIT Sloan Management Review showing that toxic corporate culture is 10.4 times as predictive of attrition as compensation.

Von Ahn’s second tip focused on proactivity, encouraging employees to solve problems rather than just complain about them. He cited the example of Duolingo’s company blog. “Early on, we didn’t have a company blog. Two engineers handled this differently,” he said. “Engineer A: Spent months complaining to me. ‘We don’t have a blog! What are you going to do about it?’ Engineer B: Came to me once and said, ‘I noticed we don’t have a blog, so I started one.’”