## Maximum sum of triplet

Provided a list of positive integers of size n. Find the maximum sum of the triplet with order list[ a] < list[ b] < list[ c] and a < b < c where a,b,c denotes the elements and list[ a ], list[ b], list[ c] denotes the position of elements.
*Input*: List [2, 4, 7, 3, 1, 9]

Hint: Here the possible triplets are

2 + 4 + 7 = 13
2 + 7 + 9 = 18
4 + 7 + 9 = 20

Hence the maximum triplet value is 20.
