Stabilize Warwick

Warwick, a human-turned-beast, has $N$ ($N \geq 3$) infusion pumps labelled from $1$ to $N$ attached to him that pumps a powerful toxin called shimmer. The $i$-th pump injects shimmer at a pressure of $P_i$. Warwick wants to ensure that all the pumps are operating at the same pressure. To achieve this, he can perform the following operation: - Choose two indices $i, j$ ($1 \leq i, j \leq N$) and