This Challenge is to find the minimum cumulative sum that traverses from row-1 thru row-N via vertical/diagonal adjacent elements of adjacent rows.

The input is a series of values of length n*(n+1)/2.

Input: S [Series that can be converted into a lower triangle]

Output: MinSum [Minimum cost path from top to bottom]

Example:

[5 7 6 3 2 5] becomes

5 0 0
7 6 0
3 2 5

Creates a MinSum of 13 [5+6+2]. The 5 can only see 6, 3 sees 7 and 6, while 2 sees 7 6 0.