A Currency System in Geraldion
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 Input
5 1 2 3 4 5
-1 题目大意： 求N个数不能组成最小的数。 分析： 这道题看起来很麻烦，其实很简单。只要看是否有1，因为前面给了范围1 ≤ ai ≤ 106,所以能给出的最小数就是1.因此N个数中有1，输出1；否则输出-1. 代码：
1 #include2 #include 3 #include 4 #include 5 using namespace std; 6 7 int n[1000]; 8 9 int main ()10 {11 int n, m;12 while(scanf("%d",&n)!=EOF)13 {14 int f=0;15 for(int i=0; i<=n; i++)16 {17 18 scanf("%d",&m);19 if (m==1) f=1;20 }21 if(f)22 printf("-1\n");23 else24 printf("1\n"); 25 }26 return 0;27 }
心得：
这道题完全要靠理解题意，题意没有理解怎么会做出题来呢？这么简单的一道题光看题就看了那么久，才理解题目的意思。经过几次比赛发现英语实在是太差了，要好好学习英语了。加油吧。