from collections import defaultdict
n = int(input())
a = list(map(int, input().split()))
m = 0
M = n
d = defaultdict(list)
for i in range(n):
	d[a[i]].append(i)
for i, j in d.items():
	if len(j) > 2:
		exit(print(0))
	if len(j) == 2:
		m = max(m, j[0])
		M = min(M, j[1])
ans = list(range(m + 1, M + 1))
print(len(ans))
print(*ans)