https://app.codesignal.com/arcade/intro/level-7/vExYvcGnFsEYSt8nQ
Consider integer numbers from 0 to n - 1 written down along the circle in such a way that the distance between any two neighboring numbers is equal (note that 0 and n - 1 are neighboring, too).
Given n and firstNumber, find the number which is written in the radially opposite position to firstNumber.
For n = 10
and firstNumber = 2
, the output should be
solution(n, firstNumber) = 7
.