import sys

n = input()
l = raw_input().split()
a = [int(i) for i in l]

d = {}

for i in a:
    if d.has_key(i):
        d[i]+=1
    else:
        d[i]=1
ans = ""
for i in d.keys():
    if d[i]%2==1:
        ans+=str(i) + ' '
print ans
