Chocolate Packaging

Background

You are preparing chocolate packages for customers. You need to accurately pack a specified weight of chocolate according to customer requirements.

Problem Description

We want to make a package of $goal$ kilos of chocolate. We have small bars (1 kilo each) and big bars (5 kilos each). Return the number of small bars to use, assuming we always use big bars before small bars. Return $-1$ if it can't be done.

Input Format

Input is given from standard input in the following format.

small big goal

Where:

• small is the number of available small chocolate bars.
• big is the number of available big chocolate bars.
• goal is the target total weight (in kilos).

Output Format

Output to standard output in the following format.

number_of_small_bars

Where number_of_small_bars is the number of small bars to use, or $-1$ if it cannot be done.

Sample

4 1 9

4

Sample Explanation

The goal is $9$ kilos. We have $1$ big bar ($5$ kilos) and $4$ small bars ($1$ kilo each). Prioritize using big bars: use $1$ big bar, remaining $9 - 5 = 4$ kilos needed. We have $4$ small bars, which is enough to provide $4$ kilos. So, $4$ small bars are needed.

4 1 10

-1

Sample Explanation

The goal is $10$ kilos. We have $1$ big bar ($5$ kilos) and $4$ small bars ($1$ kilo each). Prioritize using big bars: use $1$ big bar, remaining $10 - 5 = 5$ kilos needed. We only have $4$ small bars, which is not enough to provide $5$ kilos. Therefore, it cannot be done, return $-1$.

4 1 7

2

Sample Explanation

The goal is $7$ kilos. We have $1$ big bar ($5$ kilos) and $4$ small bars ($1$ kilo each). Prioritize using big bars: use $1$ big bar, remaining $7 - 5 = 2$ kilos needed. We have $4$ small bars, which is enough to provide $2$ kilos. So, $2$ small bars are needed.

Constraints

No additional constraints. Input data is guaranteed to be within standard integer types.