Sponsored
Use these hints if you're stuck. Try solving on your own first.
The problem can be reworded as, giving a set of points on a 2d-plane, return the geometric median.
Loop over each triplet of points (positions[i], positions[j], positions[k]) where i < j < k, get the centre of the circle which goes throw the 3 points, check if all other points lie in this circle.