货币体系

Description

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 called unfortunate. 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 numbers a₁, a₂, ..., a_n (1 ≤ a_i ≤ 10⁶) — the values of the banknotes.

Output

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

Sample Input

Input

5 
1 2 3 4 5

Output

-1

题意：求n个整数不能组成的最小整数，如果都存在，输出-1.

思路：如果n个数中有1，则都能组成，输出-1，否则不能组成的最小整数1，输出1.

  英文不好  一直看不懂题意 也是日了狗了.....

代码如下：

#include <iostream>
using namespace std;
int a[1005];
int main()
{
    int n;
    while(cin>>n)
    {
        int flag=0;
        for(int i=0;i<n;i++)
        {
            cin>>a[i];
            if(a[i]==1)
                flag=1;
        }
       
        if(flag)
            cout<<-1<<endl;
        else
            cout<<1<<endl;
    }
    return 0;
}