R to L addition exclusion

Unless it’s a 15+ letter word that ends in U, this one won’t work

I was trying to highlight where the letters we already had were.  I was trying to conceptualize various ideas about vulnerabilities in foursquares and then realized none of that matters if you can’t find a good keyword.  The problem is in how you fill the table after your keyword.  The U in that position means that you cannot correctly fill your foursquare encryption/decryption charts.

-Kryptosfan