>Math 55 is a two-semester long first-year undergraduate mathematics course at Harvard University

>The Harvard University Mathematics department claims that "This is probably the most difficult undergraduate math class in the country."

>Problem sets are expected to take from 24 to 60 hours per week to complete.[1]

>for the class of 2009: "51 students the first day, 31 students the second day, 24 for the next four days, 23 for two more weeks, and then 21 for the rest of the first semester."[4]