The Guys I Want to Catch

Four rookie cops in Noryangjin, who failed their police exams, are known to all as ‘The F-4’. That’s ‘F’, as in ‘Failure’. Witness them pursuing criminals who have violated the law in varying ways. Do the bad guys even need to worry ‘The F-4’ is hot on their trails?!
(Source: Soompi; Edited by Lee C)