MathNet 1975 — Part 01 Question 2

For each real number $r$, $[r]$ denotes the largest integer less than or equal to $r$, e.g., $[6] = 6$, $[\pi] = 3$, $[-1.5] = -2$. Indicate on the $(x, y)$-plane the set of all points $(x, y)$ for which $[x]^2 + [y]^2 = 4$.