B"An atom of element X can exist in n distinct states with energies E1 xe2 x80 x89< xe2 x80 x89E2 xe2 x80 x89< xe2 x80 x89... xe2 x80 x89< xe2 x80 x89En. Arkady wants to build a laser on this element, using a three-level scheme. Here is a simplified description of the scheme. Three distinct states i, j and k are selected, where i xe2 x80 x89< xe2 x80 x89j xe2 x80 x89< xe2 x80 x89k. After that the following process happens: Let's define the energy conversion efficiency as , i. e. the ration between the useful energy of the photon and spent energy. Due to some limitations, Arkady can only choose such three states that Ek xe2 x80 x89- xe2 x80 x89Ei xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89U. Help Arkady to find such the maximum possible energy conversion efficiency within the above constraints. The first line contains two integers n and U (3 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89n xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89105, 1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89U xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89109) -- the number of states and the maximum possible difference between Ek and Ei. The second line contains a sequence of integers E1, xe2 x80 x89E2, xe2 x80 x89..., xe2 x80 x89En (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89E1 xe2 x80 x89< xe2 x80 x89E2... xe2 x80 x89< xe2 x80 x89En xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89109). It is guaranteed that all Ei are given in increasing order. If it is not possible to choose three states that satisfy all constraints, print -1. Otherwise, print one real number xce xb7 -- the maximum possible energy conversion efficiency. Your answer is considered correct its absolute or relative error does not exceed 10 xe2 x80 x89- xe2 x80 x899. Formally, let your answer be a, and the jury's answer be b. Your answer is considered correct if . In the first example choose states 1, 2 and 3, so that the energy conversion efficiency becomes equal to . In the second example choose states 4, 5 and 9, so that the energy conversion efficiency becomes equal to . "...