### Problem Statement

You are a guitar player and you like to play your guitars, but unfortunately, you broke n strings. Therefore, you have to buy new strings to replace them, and you want to spend as little money as possible. For each brand of strings, you can choose to buy either a package of 6 strings, or 1 or more single strings.

You are given a String[] stringCosts, each element of which represents a single brand. Each element is formatted as "PACKAGE SINGLE" (quotes for clarity only), where PACKAGE is the price of a package of 6 strings and SINGLE is the price of a single string. Return the minimum amount of money required to buy at least n strings.

### Definition

 Class: BrokenStrings Method: buyStrings Parameters: int, String[] Returns: int Method signature: int buyStrings(int n, String[] stringCosts) (be sure your method is public)

### Notes

-You are allowed to buy strings from different brands (it sometimes might even be needed to get the lowest price).
-A package just contains 6 equal strings, so 1 package could be replaced by 6 single strings.

### Constraints

-n will be between 1 and 100, inclusive.
-stringCosts will contain between 1 and 50 elements, inclusive.
-Each element of stringCosts will be formatted as "PACKAGE SINGLE" (quotes for clarity only).
-Each PACKAGE will be an integer between 0 and 1000, inclusive, with no extra leading zeroes.
-Each SINGLE will be an integer between 0 and 1000, inclusive, with no extra leading zeroes.

### Examples

0)

 `4` ```{"12 3", "15 4"}```
`Returns: 12`
 You can choose to buy 1 package of the first brand, or 4 single strings. The price you pay will be 12 in both cases.
1)

 `17` `{"12 3"}`
`Returns: 36`
 The best option is to buy 3 packages (so you have 18 strings).
2)

 `7` ```{"10 3", "12 2"}```
`Returns: 12`
 Here you buy a package for 10, and another single string for 2 (from another brand) to get the lowest total price.
3)

 `9` ```{"21 25","77 23","23 88","95 43","96 19","59 36", "80 13","51 24","15 8","25 61","21 22","3 9", "68 68","67 100","83 98","96 57"}```
`Returns: 6`

#### Problem url:

http://www.topcoder.com/stat?c=problem_statement&pm=7748

#### Problem stats url:

http://www.topcoder.com/tc?module=ProblemDetail&rd=13676&pm=7748