
There are n piles of coins on a table. Each pile consists of a positive number of coins of assorted denominations.
In one move, you can choose any coin on top of any pile, remove it, and add it to your wallet.
Given a list piles , where piles[i] is a list of integers denoting the composition of the i ^th pile from top to bottom , and a positive integer k , return the maximum total value of coins you can have in your wallet if you choose exactly k coins optimally .
n == piles.length1 <= n <= 10001 <= piles[i][j] <= 10 ^51 <= k <= sum(piles[i].length) <= 2000