A portion of the graph of is shown in red below, where is a quadratic function. The distance between grid lines is unit.
What is the sum of all distinct numbers x such that f(f(f(x)))=-3?
Link to the graph: https://latex.artofproblemsolving.com/a/5/5/a55ff48c3dfe700194d16e1a80c027d03e698b32.png
