N = int(input())

s2 = input()

t = s2.split(" ")

print(len(set(t)))

lis = []

for i in t :

if i not in lis :
    lis.append(i)

lis2 = []

for i in lis:

lis2.append(int(i))

lis2.sort()

for i in range(len(lis2)):

print(lis2[i], end=" ")