Largest Number not Expressible as Sum of Multiples of 23 and 28

Theorem
The largest integer $n$ that cannot be expressed in the form:
 * $n = 23 x + 28 y$

for $x, y \in \Z_{>0}$ is $593$.

Proof
By Largest Number not Expressible as Sum of Multiples of Coprime Integers, the largest such number is:
 * $\paren {23 - 1} \times \paren {28 - 1} - 1 = 593$