output_description: Print the maximum possible number of i such that a_i=X.
  
  * * *
input_description: The input is given from Standard Input in the following format:
  
      
      
      N
      a_1 a_2 .. a_N
attempt: #!usr/bin/env python3
  from collections import defaultdict
  from collections import deque
  from heapq import heappush, heappop
  import sys
  import math
  import bisect
  import random
  
  
  def LI():
      return list(map(int, sys.stdin.readline().split()))
  
  
  def I():
      return int(sys.stdin.readline())
  
  
  def LS():
      return list(map(list, sys.stdin.readline().split()))
  
  
  def S():
      return list(sys.stdin.readline())[:-1]
  
  
  def IR(n):
      l = [None for i in range(n)]
      for i in range(n):
          l[i] = I()
      return l
  
  
  def LIR(n):
      l = [None for i in range(n)]
      for i in range(n):
          l[i] = LI()
      return l
  
  
  def SR(n):
      l = [None for i in range(n)]
      for i in range(n):
          l[i] = S()
      return l
  
  
  def LSR(n):
      l = [None for i in range(n)]
      for i in range(n):
          l[i] = SR()
      return l
  
  
  mod = 1000000007
  
  # A
  
  # B
  
  # C
  n = I()
  d = defaultdict(int)
  a = LI()
  for i in a:
      d[i] += 1
      d[i + 1] += 1
      d[i - 1] += 1
  d = list(d.values())
  print(max(d))
  # D
  
  # E
  
  # F
  
  # G
  
  # H
  
  # I
  
  # J
  
  # K
  
  # L
  
  # M
  
  # N
  
  # O
  
  # P
  
  # Q
  
  # R
  
  # S
  
  # T
  
problem_description: Statement
  
  You are given an integer sequence of length N, a_1,a_2,...,a_N.
  
  For each 1≤i≤N, you have three choices: add 1 to a_i, subtract 1 from a_i or
  do nothing.
  
  After these operations, you select an integer X and count the number of i such
  that a_i=X.
  
  Maximize this count by making optimal choices.
samples: [{"input": "7\n    3 1 4 1 5 9 2", "output": "4\n    \n\nFor example, turn the sequence into 2,2,3,2,6,9,2 and select X=2 to obtain 4,\nthe maximum possible count.\n\n* * *"}, {"input": "10\n    0 1 2 3 4 5 6 7 8 9", "output": "3\n    \n\n* * *"}, {"input": "1\n    99999", "output": "1"}]