Given a nested list of integers, return the sum of all integers in the list weighted by their depth.

Each element is either an integer, or a list – whose elements may also be integers or other lists.

Example 1:
Given the list

[[1,1],2,[1,1]]

return

10 (four 1’s at depth 2, one 2 at depth 1)

Example 2:
Given the list

[1,[4,[6]]]

return

27 (one 1 at depth 1, one 4 at depth 2, and one 6 at depth 3; 1 + 4*2 + 6*3 = 27)