Anna is working in an amusement park and she is in charge of building the railroad for a new roller coaster. She has already designed **n** special sections (conveniently numbered from $0$ to $n - 1$ that affect the speed of a roller coaster train. She now has to put them together and propose a final design of the roller coaster. For the purpose of this problem you may assume that the length of the train is zero. For each $i$ between $0$ and $n - 1$, inclusive, the special section has two properties: \begin{itemize} \item when entering the section, there is a speed limit: the speed of the train must be less or equal to $s_i$ km/h (kilometers per hour), \item when leaving the section, the speed of the train is exactly $t_i$ km/h, regardless of the speed at which the train entered the section. \end{itemize} The finished roller coaster is a single railroad line that contains the $n$ special sections in some order. Each of the $n$ sections should be used exactly once. Consecutive sections are connected with tracks. Anna should choose the order of the $n$ sections and then decide the lengths of the tracks. The length of a track is measured in meters and may be equal to any non-negative integer (possibly zero). Each meter of the track between two special sections slows the train down by $1$ km/h. At the beginning of the ride, the train enters the first special section in the order selected by Anna, going at $1$ km/h. The final design must satisfy the following requirements: \begin{itemize} \item the train does not violate any speed limit when entering the special sections; \item the speed of the train is positive at any moment. \end{itemize} Your task is to find the minimum possible total length of tracks between sections. \InputFile First line contains number $n~(2 \le n \le 2 \cdot 10^5)$. Each of the next $n$ lines contains numbers $s_i$ and $t_i~(1 \le i \le n, 1 \le s_i, t_i \le 10^9)$. \OutputFile Print the minimum possible total length of all tracks between sections.