CF629B Far Relative’s Problem

Famil Door wants to celebrate his birthday with his friends from Far Far Away. He has $ n $ friends and each of them can come to the party in a specific range of days of the year from $ a_{i} $ to $ b_{i} $ . Of course, Famil Door wants to have as many friends celebrating together with him as possible. Far cars are as weird as Far Far Away citizens, so they can only carry two people of opposite gender, that is exactly one male and one female. However, Far is so far from here that no other transportation may be used to get to the party. Famil Door should select some day of the year and invite some of his friends, such that they all are available at this moment and the number of male friends invited is equal to the number of female friends invited. Find the maximum number of friends that may present at the party.

The first line of the input contains a single integer $ n $ ( $ 1

Print the maximum number of people that may come to Famil Door's party.

In the first sample, friends $ 3 $ and $ 4 $ can come on any day in range $ [117,128] $ . In the second sample, friends with indices $ 3 $ , $ 4 $ , $ 5 $ and $ 6 $ can come on day $ 140 $ .