from collections import Counter

n = int(input())
a = [int(x) for x in input().split()]

cnt = Counter(a)

if any(cnt[x] >= 3 for x in a):
	print("0\n")
	exit()
	
left = {}
right = {}

for i in range(n):
	left[~a[i]] = i
	right[a[i]] = i

p = -1
q = n

for x in a:
	if left[x] == right[x]:
		continue
	p = max(left[x], p)
	q = min(right[x], q)
	
r = range(p + 1, q)

print(len(r))
print(*r)