(VAR X X1 X2 X3 Y )
(RULES 
        active(minus(0, Y)) -> mark(0)
        active(minus(s(X), s(Y))) -> mark(minus(X, Y))
        active(geq(X, 0)) -> mark(true)
        active(geq(0, s(Y))) -> mark(false)
        active(geq(s(X), s(Y))) -> mark(geq(X, Y))
        active(div(0, s(Y))) -> mark(0)
        active(div(s(X), s(Y))) -> mark(if(geq(X, Y), s(div(minus(X, Y), s(Y))), 0))
        active(if(true, X, Y)) -> mark(X)
        active(if(false, X, Y)) -> mark(Y)
        active(s(X)) -> s(active(X))
        active(div(X1, X2)) -> div(active(X1), X2)
        active(if(X1, X2, X3)) -> if(active(X1), X2, X3)
        s(mark(X)) -> mark(s(X))
        div(mark(X1), X2) -> mark(div(X1, X2))
        if(mark(X1), X2, X3) -> mark(if(X1, X2, X3))
        proper(minus(X1, X2)) -> minus(proper(X1), proper(X2))
        proper(0) -> ok(0)
        proper(s(X)) -> s(proper(X))
        proper(geq(X1, X2)) -> geq(proper(X1), proper(X2))
        proper(true) -> ok(true)
        proper(false) -> ok(false)
        proper(div(X1, X2)) -> div(proper(X1), proper(X2))
        proper(if(X1, X2, X3)) -> if(proper(X1), proper(X2), proper(X3))
        minus(ok(X1), ok(X2)) -> ok(minus(X1, X2))
        s(ok(X)) -> ok(s(X))
        geq(ok(X1), ok(X2)) -> ok(geq(X1, X2))
        div(ok(X1), ok(X2)) -> ok(div(X1, X2))
        if(ok(X1), ok(X2), ok(X3)) -> ok(if(X1, X2, X3))
        top(mark(X)) -> top(proper(X))
        top(ok(X)) -> top(active(X))
        
)