RU-ALLRUSSIAN 1968 Problem 16

$\{\mathrm{a_i}\}$ and $\{\mathrm{b_i}\}$ are permutations of $\{1 / 1,1 / 2,\dots ,1 / \mathrm{n}\}$ . $\mathrm{a_1 + b_1\geq a_2 + b_2\geq \ldots \geq a_n + b_n}$ . Prove that for every m $(1\leq \mathrm{m}\leq \mathrm{n})$ $\mathrm{a_m + a_n\geq 4 / m}$