In Łukasiewicz's 3-valued logic, the truth values are $0$ (False), $\frac{1}{2}$ (Neutral), and $1$ (True). The truth value of the implication $P \to Q$ is defined as $v(P \to Q) = \min(1, 1 - v(P) + v(Q))$. How many of the $3^3 = 27$ possible truth assignments to the propositional variables $(P, Q, R)$ satisfy $v(P \to (Q \to R)) = 1$?