#!/bin/ruby

n = gets.strip.to_i
a = gets.strip.split(' ').map(&:to_i)

answer = 0

a.each_with_index do |outer,o|
  same = 0
  bigger = 0
  smaller = 0
  a.each_with_index do |inner,i|
    if outer - inner == 0
      same += 1
    elsif 0 < (outer - inner) && (outer - inner) < 2
      smaller += 1
    elsif 0 < (inner - outer) && (inner - outer) < 2
      bigger += 1
    end
  end
  temp = bigger > smaller ? (same + bigger) : (same + smaller)
  if temp > answer
    answer = temp
  end
end

p answer