WA9 happens when in attempt of optimization you try to convert the name of an option into int64, but miserably fail at that.
Like, (1..26)27^0 + (1..26)27^1 + (1..26)27^2 + ...
I simply forgot the increment, so i had (1..26)27^0 + (1..26)27^0 + (1..26)27^0 + ...