import io
import sys
from collections import defaultdict, deque, Counter
from itertools import permutations, combinations, accumulate
from heapq import heappush, heappop
from bisect import bisect_right, bisect_left
from math import gcd
import math

_INPUT = """\
6
7
3 5 4 3 2 1 9
4
1 1 2 2
5
1 2 3 4 5
3
1 1 1
12
4 8 9 10 3 6 4 2 1 7 11 9
"""

def input():
  return sys.stdin.readline()[:-1]

def solve(test):
  N=int(input())
  A=list(map(int, input().split()))
  ans=[]
  Y=defaultdict(int)
  for i in range(N):
    Y[A[i]]+=1
  two=set([key for key in Y if Y[key]==2])
  three=[key for key in Y if Y[key]>=3]
  if len(three)>0:
    # print('x')
    print(len(ans))
    print(*ans)
  else:
    now=0
    tmp=two.copy()
    while now<N-1:
      if A[now] in tmp and A[now] in two:
        tmp.remove(A[now])
        now+=1
      elif A[now] not in tmp and A[now] in two:
        break
      else:
        now+=1
      if len(tmp)==0: ans.append(now)
    print(len(ans))
    print(*ans)

def random_input():
  from random import randint,shuffle
  N=randint(1,10)
  M=randint(1,N)
  A=list(range(1,M+1))+[randint(1,M) for _ in range(N-M)]
  shuffle(A)
  return (" ".join(map(str, [N,M]))+"\n"+" ".join(map(str, A))+"\n")*3

def simple_solve():
  return []

def main(test):
  if test==0:
    solve(0)
  elif test==1:
    sys.stdin = io.StringIO(_INPUT)
    case_no=int(input())
    for _ in range(case_no):
      solve(0)
  else:
    for i in range(1000):
      sys.stdin = io.StringIO(random_input())
      x=solve(1)
      y=simple_solve()
      if x!=y:
        print(i,x,y)
        print(*[line for line in sys.stdin],sep='')
        break

#0:提出用、1:与えられたテスト用、2:ストレステスト用
main(0)