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:
when entering the section, there is a speed limit: the speed of the train must be less or equal to si km/h (kilometers per hour),
when leaving the section, the speed of the train is exactly ti km/h, regardless of the speed at which the train entered the section.
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:
the train does not violate any speed limit when entering the special sections;
the speed of the train is positive at any moment.
Your task is to find the minimum possible total length of tracks between sections.
First line contains number n (2≤n≤2⋅105). Each of the next n lines contains numbers si and ti (1≤i≤n,1≤si,ti≤109).
Print the minimum possible total length of all tracks between sections.