Logical implication with the S letter doesn't work

[fflakito]

It seems to work just fine with most letters but I tried with S and got this:

Enjoy! -> 3+4 > 2
true
Enjoy! -> P -> Q
Defined: P -> Q is TRUE
Enjoy! -> R -> S
I'm so sorry, something wrong. Please feel free to report this.
Enjoy! -> R->S
I'm so sorry, something wrong. Please feel free to report this.
Enjoy! -> P -> Q
Defined: P -> Q is TRUE
Enjoy! -> Q -> R
Defined: Q -> R is TRUE
Enjoy! -> R -> S
I'm so sorry, something wrong. Please feel free to report this.
Enjoy! -> A -> B
Defined: A -> B is TRUE
Enjoy! -> B -> S
I'm so sorry, something wrong. Please feel free to report this.
Enjoy! -> B -> T
Defined: B -> T is TRUE
Enjoy! -> S -> T
I'm so sorry, something wrong. Please feel free to report this.

Is it just me ?

[fflakito]

PS : I am new to programming, please be easy on me, よろしくお願いします ! :)
I didn't notice similar issues, so I submitted this one.

[gogotanaka]

@FrenchFlakito Thank you so much! You'er right. Actually word S is reserved for Integral.
I have to say sorry about there is no prefer document..!
Before preparing anything, this language become little bit famous... there are many thing I need to do.

Anyway, sorry about that, I'm gonna make prefer docs!

thanks.