B"Let's assume that we have a sequence of doubles a1, xe2 x80 x89a2, xe2 x80 x89..., xe2 x80 x89a|a| and a double variable x. You are allowed to perform the following two-staged operation: Let's use function g(a, xe2 x80 x89x) to represent the largest value that can be obtained from variable x, using the described operation any number of times and sequence a. Sereja has sequence b1, xe2 x80 x89b2, xe2 x80 x89..., xe2 x80 x89b|b|. Help Sereja calculate sum: . Record [bi, xe2 x80 x89bi xe2 x80 x89+ xe2 x80 x891, xe2 x80 x89..., xe2 x80 x89bj] represents a sequence containing the elements in brackets in the given order. To avoid problems with precision, please, print the required sum divided by |b|2. The first line contains integer |b| (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89|b| xe2 x80 x89 xe2 x89 xa4 xe2 x80 x893 xc2 xb7105) -- the length of sequence b. The second line contains |b| integers b1, b2, ..., b|b| (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89bi xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89105). In a single line print a real number -- the required sum divided by |b|2. Your answer will be considered correct if its absolute or relative error won't exceed 10 xe2 x80 x89- xe2 x80 x896."...