B"You are given a tree (an undirected connected graph without cycles) and an integer s . Vanya wants to put weights on all edges of the tree so that all weights are non-negative real numbers and their sum is s . At the same time, he wants to make the diameter of the tree as small as possible. Let's define the diameter of a weighed tree as the maximum sum of the weights of the edges lying on the path between two some vertices of the tree. In other words, the diameter of a weighed tree is the length of the longest simple path in the tree, where length of a path is equal to the sum of weights over all edges in the path. Find the minimum possible diameter that Vanya can get. The first line contains two integer numbers n and s ( 2 <= q n <= q 10^5 , 1 <= q s <= q 10^9 ) -- the number of vertices in the tree and the sum of edge weights. Each of the following n xe2 x88 x921 lines contains two space-separated integer numbers a_i and b_i ( 1 <= q a_i, b_i <= q n , a_i neq b_i ) -- the indexes of vertices connected by an edge. The edges are undirected. It is guaranteed that the given edges form a tree. Print the minimum diameter of the tree that Vanya can get by placing some non-negative real weights on its edges with the sum equal to s . Your answer will be considered correct if its absolute or relative error does not exceed 10^{-6} . Formally, let your answer be a , and the jury's answer be b . Your answer is considered correct if frac {|a-b|} {max(1, b)} <= q 10^{-6} . In the first example it is necessary to put weights like this: It is easy to see that the diameter of this tree is 2 . It can be proved that it is the minimum possible diameter. In the second example it is necessary to put weights like this: "...