Study the pattern below carefully. If the pattern continues, what is the $99^{\text{th}}$ letter? $\begin{matrix} \text{S} & \text{Q} & \text{U} & \text{A} & \text{R} & \text{E} & \text{S} & \text{Q} & \text{U} & \text{A} & \text{R} & \text{E} & \text{S} & \text{Q} & \text{U} & \text{A} & \text{R} & \text{E} & \dots \\ 1^{\text{st}} & & & & & & & & & & & & & & & & & 18^{\text{th}} \end{matrix}$ Ans : ___