从非负整数序列 0, 1, 2, ..., n中给出包含其中n个数的子序列,请找出未出现在该子序列中的那个数。
n, *number_list = [*map(int, input().split())] number_list = set(number_list) all_number_list = {number for number in range(n + 1)} print((all_number_list - number_list).pop())