(VAR x y )
(RULES 
        \(x, x) -> e
        /(x, x) -> e
        .(e, x) -> x
        .(x, e) -> x
        \(e, x) -> x
        /(x, e) -> x
        .(x, \(x, y)) -> y
        .(/(y, x), x) -> y
        \(x, .(x, y)) -> y
        /(.(y, x), x) -> y
        /(x, \(y, x)) -> y
        \(/(x, y), x) -> y
        
)