n = int(input()) arr = list(map(int,input().strip().split())) arr.sort() tag = True for i in range(1,len(arr),2): if arr[i] == arr[i - 1]: continue else: tag = False print(arr[i - 1]) break if tag: print(arr[-1])
n = int(input()) arr = list(map(int,input().strip().split())) arr.sort() tag = True for i in range(1,len(arr),2): if arr[i] == arr[i - 1]: continue else: tag = False print(arr[i - 1]) break if tag: print(arr[-1])