题目描述
Takahashi has N days of summer vacation.
His teacher gave him M summer assignments. It will take A_i days for him to do the i-th assignment.
He cannot do multiple assignments on the same day, or hang out on a day he does an assignment.
What is the maximum number of days Takahashi can hang out during the vacation if he finishes all the assignments during this vacation?
If Takahashi cannot finish all the assignments during the vacation, print -1 instead.
Constraints
- $1 \leq N \leq 10^6$
- $1 \leq M \leq 10^4$
- $1 \leq A_i \leq 10^4$
Input
Input is given from Standard Input in the following format:
N M
A_1 ... A_M
Output
Print the maximum number of days Takahashi can hang out during the vacation, or -1.
Examples
Input
41 2
5 6
Output
30
Input
10 2
5 6
Output
-1
Input
11 2
5 6
Output
0
Input
314 15
9 26 5 35 8 9 79 3 23 8 46 2 6 43 3
Output
9
输入格式
见题面
输出格式
见题面