LonelyInteger

 1 def main(): 2     n = int(raw_input()) 3     s = dict() 4     a = 0 5  6     arr = map(int,raw_input().strip().split()) 7     for _ in range(n): 8         num = arr[_] 9         if not s.get(num):10             s.update({num:1})11         else:12             a = s.get(num)13             a += 114             s.update({num:a})15 16     for i in s:17         if s.get(i) % 2 != 0:18             PRint i19             break20 21 main()

1 #!/usr/bin/py2 def lonelyinteger(a):3     answer = 04     answer = reduce(lambda x,y: x^y, a)5     return answer6 if __name__ == '__main__':7     a = input()8     b = map(int, raw_input().strip().split(" "))9     print lonelyinteger(b)