Kata

Complete the function that takes an array of words.

You must concatenate the nth letter from each word to construct a new word which should be returned as a string, where n is the position of the word in the list.

For example:

["yoda", "best", "has"]  -->  "yes"
  ^        ^        ^
  n=0     n=1     n=2

Note: Test cases contain valid input only - i.e. a string array or an empty array; and each word will have enough letters.