Positive Solutions to Linear Diophantine Equation

I've been looking at the following problem, involving Diophantine equations:

Let such that and . Show that there exist nonnegative integers so that .

I know that the solutions to a linear Diophantine equation are given by , where is a particular solution and is an integer parameter. If I want these to be positive simultaneously, I need to have . In other words, there needs to be an integer in the interval .

From here, I cannot seem to put bounds on the endpoints of the interval. I would appreciate any insight you may have on the issue.