
n = int(input())
ns = map(int, input().strip().split(' '))

x = {}

for num in ns:
    if not num in x:
        x[num] = 1
    else:
        x[num] += 1

a = []
for k, v in x.items():
    if v % 2 == 1:
        a.append(str(k))

print(' '.join(a))
