gets
a = gets.split.map(&:to_i)
l = 0
h = {} #前回出現位置
max = 0
a.each_with_index do |n, r|
  l = [l, h[n] + 1].max if h[n]
  m = r - l + 1
  max = m if m > max
  h[n] = r
end

puts max