x = [13, 5, 6, 2, 5]
y = [5, 2, 5, 13]

list = [0]*2010
for i in x:
    list[i+1000] = list[i+1000]+1
for i in y:
    list[i+1000] = list[i+1000]+1
for i in range(len(list)):
    if list[i]%2==1: print i+1000