Let $A$ be a set of numbers chosen from $1, 2, \ldots, 2015$ with the property that any two distinct numbers, say $x$ and $y$, in $A$ determine a unique isosceles triangle (which is non-equilateral) whose sides are of length $x$ or $y$. What is the largest possible size of $A$?

Let's think step by step and output the final answer within \boxed{}.
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