https://mirror.codeforces.com/problemset/problem/1307/D

I have elements 1 to N. Each element has two values xi and yi (1<=i<=N). Now I want to choose two elements a,b such that min(xa+yb,xb+ya) is maximized. There is a naive n^2 solution to check every pair of elements. But it is possible to do it in nlogn complexity. The problem link mentioned above has the editorial that describes the method but I couldn't get it. Can anyone explain ?