NextPermutationOnSubsegment

Implemented a data structure that allows:

1. find the sum on the subsegment [l,r]
2. insert element x at position pos
3. remove the element x located at position i
4. to assign the element x on the subsegment [l, r]
5. add the number x on the subsegment [l, r]
6. next_permutation on the subsegment [l, r]
7. prev_permutation on the [l, r] subsegment.

All operations work for O(logn) This structure works on Splay-tree with