You "cram like crazy". It is a very common expression among Korean students, as most of them do it one time or another, or every test time for some, in their school years. Korea is known for high academic pressures on the students, from kindergarten to college :-)

That means you study for an exam before a few days of the exam day. 내일이 시험인데, 나는 벼락치기를 했다.