B"Vanya walks late at night along a straight street of length l, lit by n lanterns. Consider the coordinate system with the beginning of the street corresponding to the point 0, and its end corresponding to the point l. Then the i-th lantern is at the point ai. The lantern lights all points of the street that are at the distance of at most d from it, where d is some positive number, common for all lanterns. Vanya wonders: what is the minimum light radius d should the lanterns have to light the whole street? The first line contains two integers n, l (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89n xe2 x80 x89 xe2 x89 xa4 xe2 x80 x891000, 1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89l xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89109) -- the number of lanterns and the length of the street respectively. The next line contains n integers ai (0 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89ai xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89l). Multiple lanterns can be located at the same point. The lanterns may be located at the ends of the street. Print the minimum light radius d, needed to light the whole street. The answer will be considered correct if its absolute or relative error doesn't exceed 10 xe2 x80 x89- xe2 x80 x899. Consider the second sample. At d xe2 x80 x89= xe2 x80 x892 the first lantern will light the segment [0, xe2 x80 x894] of the street, and the second lantern will light segment [3, xe2 x80 x895]. Thus, the whole street will be lit."...