57. There is a sequence of numbers, the first number is 1, the second number is 3, starting from the third number, each number is the unit digit of the sum of the two preceding numbers: $1,3,4,7,1,8,9,7,6$, $\qquad$ In this sequence, take 2019 consecutive numbers, such that the sum of these 2019 numbers is maximized, this maximum sum is $\qquad$.
Reference answer: 10104
Exam point: Application problem - Periodic problem