Let $R$ be an integral domain , $S$ be a subring of $R[x_1,..., x_n]$ .
If $S$ contains two polynomials of relatively prime degree, then how to show that there exists an integer $m>1$ such that $S$ contains a polynomial of degree $l$ for every $l>m$ ?
I can easily show the claim for $n=1$, but having difficulty in showing for higher $n$. Please help.