Codeforces Round #313 Currency System in Geraldion （枚举）-优快云博客

探讨了在一个使用特定面额纸币的魔法岛屿上，如何找出无法用任何数量的这些纸币组合而成的最小金额。通过输入不同面额的纸币值，程序能够快速判断是否存在无法构成的最小金额。

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, ..., 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

解析：只要判断有没有 1 即可，若有 1 ，则无unfortunate sum，若没有1，则最小的unfortunate sum就为1。

代码：

#include<cstdio>
using namespace std;

int main()
{
  int i,j,k,n;
  scanf("%d",&n);
  for(i=1;i<=n;i++)
    {
      scanf("%d\n",&k);
      if(k==1){printf("-1");return 0;}
	}
  printf("1\n");
  return 0;
}