import strutils, sequtils, algorithm, math


var
  n = readLine(stdin).parseInt()
  a_seq = readLine(stdin).split(' ').map(parseInt)
  inchworm = newSeq[int](1_000_002)
  right, tmp_a : int
  left, max_len = 0

for right in countup(1, n):
  tmp_a = a_seq[right - 1]
  if inchworm[tmp_a] > 0:
    left = max(inchworm[tmp_a], left)
  max_len = max(max_len, right - left)
  inchworm[tmp_a] = right

echo(max_len)