# frozen_string_literal: true

# @see https://yukicoder.me/submissions/14249 by yuki2006
# rubocop:todo Metrics/AbcSize
def solve # rubocop:todo Metrics/MethodLength
  l = 0
  r = 0
  m = 0
  c = Array.new(10**6 + 1, false)

  while r < N
    if c[D[r]]
      m = [m, r - l].max
      c[D[l]] = false
      l += 1
    else
      c[D[r]] = true
      r += 1
    end
  end

  [m, r - l].max
end
# rubocop:enable Metrics/AbcSize

N = gets.to_i
D = gets.chomp.split.map(&:to_i)

puts solve