Suppose $R$ is a UFD.Let $a \in R$.Then it can be represented as a finite product of irreducible elements as $a = {p_{1}}^{r_{1}}{p_{2}}^{r_{2}}...{p_{n}}^{r_{n}}$, where $p_{i}$ are irreducible.Now how can show that ${p_{i}}^{k_{i}}$ cannot divide $a$ for $k_{i} > r_{i}$ for $i = 1,2,...,n$.Please help me.
Thank you in advance.