I see what you mean. All four joined in the same month, all attend the same university, all have roughly the same number of accepted solutions, and number of submissions, and the number of submissions is way higher than any others I’ve seen.
They’re also submitting to many different problems within a few minutes of the previous. They also submit wrong answers to problems where they’ve already been accepted.
All very curious, if not suspicious.
Ah… an idea… I suspect they’re bots outsourcing the validation of submissions from an internal online judge. Strange names if that’s the case though.