5. Xiao Hua plays a certain game, in each round he can play as many times as he wants, each time the score is one of the three numbers: $8, a$ (a natural number), 0. The total score of each round is called the total points of that round. Xiao Hua has once achieved the following total points: $103,104,105,106,107,108,109,110$, and it is known that he cannot achieve the total points of “83 points”. What is $a$?