An arcade redemption counter lets a player turn in ticket stubs for prizes, but only if every stub in the turned-in pile comes from one of at most two point-value tiers, and those two tiers must be exactly 1 point apart (for example, tiers worth 4 and 5, but not tiers worth 4 and 6, and not a single tier alone). Given the point values printed on a roll of n ticket stubs, find the largest possible pile of stubs (choosing any subset of the stubs, not necessarily consecutive on the roll) that uses stubs from exactly two point-value tiers whose values differ by exactly 1.

Input format

• Line 1: a single integer n, the number of ticket stubs.
• Line 2: n space-separated integers, the point value printed on each stub, in the order they were torn from the roll.

Output format

Print a single integer: the maximum number of stubs in a pile that uses stubs from exactly two distinct point-value tiers differing by exactly 1. If no two stubs have point values differing by exactly 1, print 0.

Constraints

• 1 <= n <= 2 * 10^5
• 1 <= point value of each stub <= 10^9

8
1 3 2 2 5 2 3 7

5

5
1 1 1 1 1

0