Given positions of N kids and M ice cream sellers on a 1D line, find the smallest distance E such that every kid lies within the range [P - E, P + E] of at least one seller.

This problem can be efficiently solved using binary search on the possible values of the distance E. For a given E, we can check if all kids are covered by at least one seller. This check can be done greedily: sort the kids and sellers, then for each kid, find the closest seller to their left that can cover them. If all kids are covered, we try a smaller E; otherwise, we need a larger E.