5320: ABC163——Task B：Homework
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Description
Takahashi has NN days of summer vacation.
His teacher gave him MM summer assignments. It will take AiAi days for him to do the ii-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.
Input
Input is given from Standard Input in the following format:
N M A1 ... AM
Output
Print the maximum number of days Takahashi can hang out during the vacation, or -1.
Constraints
- 1≤N≤1061≤N≤106
- 1≤M≤1041≤M≤104
- 1≤Ai≤104
Sample 1 Input
41 2
5 6
Sample 1 Output
30
For example, he can do the first assignment on the first 55 days, hang out on the next 3030 days, and do the second assignment on the last 66 days of the vacation. In this way, he can safely spend 3030 days hanging out.
Sample 2 Input
10 2
5 6
Sample 2 Output
-1
He cannot finish his assignments.
Sample 3 Input
11 2
5 6
Sample 3 Output
0
He can finish his assignments, but he will have no time to hang out.
HINT
【样例 4 输入】
AtCoder Beginner Contest 163，Task B。https://atcoder.jp/contests/abc163/tasks/abc163_b
314 15 9 26 5 35 8 9 79 3 23 8 46 2 6 43 3【样例 4 输出】
9【题目出处】
AtCoder Beginner Contest 163，Task B。https://atcoder.jp/contests/abc163/tasks/abc163_b