The well-known mobile network operator Totalphone has set up a number of new base transceiver stations in order to cover a newly-built highway with its network. As always the programmers of Totalphone have been sloppy; as a result, the transmission power cannot be set up individually for the stations, but one can only set the transmission power to a fixed common value for all the stations. In order to minimize power consumption, the company wants to know the maximal distance of a point on the highway to the nearest base transceiver station. \InputFile The first line of input file consists of two integers \textbf{N} (\textbf{1} ≤ \textbf{N} ≤ \textbf{10^6}) and \textbf{L} (\textbf{1} ≤ \textbf{L} ≤ \textbf{10^9}) representing the number of base transceiver stations and the length of the highway, respectively. \textbf{N} lines follow, each containing a pair of integers\textbf{x_i}, \textbf{y_i} (\textbf{-10^9} ≤ \textbf{x_i}, \textbf{y_i} ≤ \textbf{10^9}) which describes the coordinates of a base transceiver station. All points are distinct. Coordinates are sorted in the non-decreasing order with respect to \textbf{x_i} coordinates. If two values of \textbf{x_i} are the same, then coordinates are sorted with respect to \textbf{y_i} coordinates in increasing order. The highway is a straight line ranging from (\textbf{0}; \textbf{0}) to (\textbf{L}; \textbf{0}). \OutputFile The first and only line of output file should contain a single number - the maximal distance of a point on the highway to the nearest base transceiver station. Your output will be regarded as correct if it differs by at most \textbf{10^\{-3\}} from the precise result.