title: Given 3 x N rectangle, determine how many ways can we tile the rectangle using 1x3 and 3x1 tiles
body: <p><img src="https://i.imgur.com/WFbP8.png" alt=""></p>
  
  <p>How might I approach this problem? I am thinking I try to put tiles, then if I cant put any more, I need to backtrack ... but how do I know how much to backtrack? Also after putting a tile, how might I (the code) decide which next tile to fill and with which type of tile?</p>