貨幣體系，國際貨幣體系

貨幣體系，國際貨幣體系

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

5 
1 2 3 4 5

-1

題意：求n個整數不能組成的最小整數，如果都存在，輸出-1.

思路：如果n個數中有1，則都能組成，輸出-1，否則不能組成的最小整數1，輸出1.

  英文不好  一直看不懂題意 也是日了狗了.....

代碼如下：

 1 #include <iostream>
 2 using namespace std;
 3 int a[1005];
 4 int main()
 5 {
 6     int n;
 7     while(cin>>n)
 8     {
 9         int flag=0;
10         for(int i=0;i<n;i++)
11         {
12             cin>>a[i];
13             if(a[i]==1)
14                 flag=1;
15         }
16        
17         if(flag)
18             cout<<-1<<endl;
19         else
20             cout<<1<<endl;
21     }
22     return 0;
23 }