Let \( p(x) \) be a monic polynomial of degree 3 with roots \( r_1, r_2, \) and \( r_3 \). Given that \( p(x) \) leaves a remainder of 2 when divided by \( x-1 \), and a remainder of -3 when divided by \( x-2 \). Find \( p(0) \). Let's think step by step and output the final answer within \boxed{}.
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