Takahashi is taking exams on N subjects. The score on each subject will be an integer between 0 and K (inclusive).
He has already taken exams on N-1 subjects and scored A_i points on the i-th subject.
His goal is to achieve the average score of M points or above on the N subjects.
Print the minimum number of points Takahashi needs on the final subject to achieve his goal.
If the goal is unachievable, print -1 instead.

-----Constraints-----
- $2 \leq N \leq 100$
- $1 \leq K \leq 100$
- $1 \leq M \leq K$
- $0 \leq A_i \leq K$
- All values in input are integers.

-----Input-----
Input is given from Standard Input in the following format:
N K M
A_1 A_2 ... A_{N-1}

-----Output-----
Print the minimum number of points required on the final subject, or -1.

-----Sample Input-----
5 10 7
8 10 3 6

-----Sample Output-----
8

If he scores 8 points on the final subject, his average score will be (8+10+3+6+8)/5 = 7 points, which meets the goal.

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