4. Kuzya the flea can make jumps from each vertex of a regular tetrahedron \(ABCD\) to the three adjacent vertices, with the choice of these vertices being random and equally probable. Kuzya started jumping from vertex \(A\) and, after 2018 jumps, ended up at vertex \(C\). What is the probability that this could happen?
Answer: $\quad P(A)=\frac{3^{2018}-1}{4 \cdot 3^{2018}}$.