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: iimport collections
  
  n=int(input())
  l=list(map(int,input().split()))
  s=collections.Counter(l)
  s=list(s.items())
  s=sorted(s,key=lambda x:x[0])
  #print(s)
  f=[0]*len(s)
  for i in range(len(s)):
      f[i]=s[i][1]
      if i>=1:
          if s[i-1][0]==s[i][0]-1:
              f[i]+=s[i-1][1]
      if i<=len(s)-2:
          if s[i+1][0]==s[i][0]+1:
              f[i]+=s[i+1][1]
  print(max(f))
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"}]