\textbf{n} segments \[\textbf{a_i}, \textbf{b_i}\] are given on a coordinate line. Find the number of pairs (\textbf{i}, \textbf{j}) such that \textbf{i} < \textbf{j} and segments \[\textbf{a_i}, \textbf{b_i}\] and \[\textbf{a_j}, \textbf{b_j}\] have at least one common point. \InputFile The first line contains an integer \textbf{n} (\textbf{1} ≤ \textbf{n} ≤ \textbf{10^5}). Each of the next \textbf{n} lines contains numbers \textbf{a_i} and \textbf{b_i} - the end points of a corresponding segment (\textbf{-10^9} ≤ \textbf{a_i}, \textbf{b_i} ≤ \textbf{10^9}). \OutputFile Print the number of pairs of intersecting segments.