Đề thi chính thức TIMO 2019 - Lớp 8 - Vòng Quốc Gia

If $\overline{abcd} + \overline{bcda} + \overline{cdab} + \overline{dabc} = 17776$, calculate $a + b + c + d$

There are 22 problems in a mathematics competition. The scores of each problem are allocated in the following ways: 3 marks will be given for a correct answer, 1 mark will be deducted from a wrong answer and 0 marks will be given for a blank answer. Find the minimum number of candidate(s) to ensure that 2 candidates will have the same scores in the competition.