You've no doubt heard both investing adages many times. But could combining the two sayings be a smart strategy by buying on stocks that dipped in May and then go away? Is it time to buy May's worst-performing S&P 500 stocks? Let's take a look. 1. EPAM Systems EPAM Systems (EPAM -0.95%) was the biggest loser in the S&P 500 last month. Shares of the information technology services provider plunged 24% in May. EPAM is now down more than 40% year to date. The May sell-off came after EPAM's first-quarter update ...