num = int(raw_input())

numlist = raw_input().split(' ')

result = []

for i in numlist:

i = int(i)

if i in result:

continue

else:

result.append(i)

result.sort()

print len(result)

s = ""

for i in result:

s += str(i)

s += ' '

s = s[:-1]

print s

可以不用转成int,直接用string就行