A recruiter plans to hire $\textbf{\textit{n}}$ people and conducts their interviews at two different locations of the company. He evaluates the cost of inviting candidates to both these locations. The plan is to invite 50% at one location, and the rest at the other location, keeping costs to a minimum.

We are given an array, costs, where $costs[i] = [aCost_i, bCost_i]$, the cost of inviting the $i^{th}$ person to City $A$ is $aCost_i$ ...