#
# 代码中的类名、方法名、参数名已经指定,请勿修改,直接返回方法规定的值即可
#
# 
# @param numbers int整型一维数组 
# @return int整型
#
class Solution:
    def duplicate(self , numbers ):
        # write code here
        n = len(numbers)
        if n == 0 or n == 1:
            return -1
        else:
            for i in range(n):
                if numbers[i] in numbers[i+1 : n]: # 切片,将当前元素和后面元素分开
                    return numbers[i] 
                    break