from sys import stdin
from collections import Counter

class Compute(object):
    def __init__(self, nums):
        self.cached = {}
        self.nums = nums
    def __call__(self, n):
        if n not in self.cached:
            print n
            print self.nums
            r = filter(lambda x: -1 <= (n - x) <= 1, self.nums)
            print r
            self.cached[n] = len(r)

stdin.readline()
nums = (int(n) for n in stdin.readline().split())
c = Counter(nums)
print max(map(lambda (k, _): max(c[k + 1], c[k - 1]) + c[k], c.items()))