【CF简单介绍】

提交链接：http://codeforces.com/contest/560/problem/A


题面：

A. Currency System in Geraldion
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output

A magic island Geraldion, where Gerald lives, has its own currency system. It uses banknotes of several values. But the problem is, the system is not perfect and sometimes it happens that Geraldionians cannot express a certain sum of money with any set of banknotes. Of course, they can use any number of banknotes of each value. Such sum is calledunfortunate. Gerald wondered: what is the minimumunfortunate sum?

Input

The first line contains number n (1 ≤ n ≤ 1000) — the number of values of the banknotes that used in Geraldion.

The second line contains n distinct space-separated numbersa1, a2, ..., an (1 ≤ ai ≤ 106) — the values of the banknotes.

Output

Print a single line — the minimum unfortunate sum. If there are no unfortunate sums, print - 1.

Sample test(s)
Input
5
1 2 3 4 5
Output
-1

















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解题：看有无1，没有1是绝对得不到1的。能够直接扫一遍，做一个标记，看1是否出现过。Hack了一个。他遇到1就停止输入，然而我却Hack失败了，由于系统仅仅判out文件....