10. The computer screen displays a series of numbers according to the following rule: if the screen displays $a, b$, then the third display is $ab-1$. Initially, the screen displays $1, 2$. Find the number displayed on the screen at the 2018th display.
10. From the problem, we know the first ten numbers displayed on the screen are
$$
1,2,1,1,0,-1,-1,0,-1,-1 \text {. }
$$

Obviously, the numbers displayed on the screen at the 8th, 9th, and 10th times are the same as those displayed at the 5th, 6th, and 7th times.
Notice that, $2018=5+671 \times 3$.
Therefore, the number displayed at the 2018th time is the same as the number displayed at the 5th time, which is 0.