Rail Fence Cipher

In Rail Fence Cipher encoding is done by by placing each character successively in a diagonal along a set of rails.

Create a function that takes two arguments; a string and the number of rails, and returns the encoded message.

message = "WEAREDISCOVEREDFLEEATONCE"
rails = 3

rail_fence_cipher(message, rails) ➞ "WECRLTEERDSOEEFEAOCAIVDEN"

In above example, given message to be decomposed in 3 rails:

W       E       C       R       L       T       E
  E   R   D   S   O   E   E   F   E   A   O   C
    A       I       V       D       E       N

Starting from upper line, encoded message will be :

"WECRLTEERDSOEEFEAOCAIVDEN"

Examples

rail_fence_cipher("WEAREDISCOVEREDFLEEATONCE", 3) ➞ "WECRLTEERDSOEEFEAOCAIVDEN"

rail_fence_cipher("INNOKODAKADEMIJAISAMAZING", 4) ➞ "EIIDTSZNAIAAGBM"

rail_fence_cipher("WEWILLALLDIEONEDAY", 3) ➞ "WLLOAEILLDENDYWAIE"

Notes

Rails will be >=2