Dearrangement Error

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As we all know the formula of dearrangement in the form of the recursive equation but Chef forgot the main equation and wrote down the following: \[ A(n)= \begin{cases} 2A(n-1) +3 A(n-2),& \text{if } n\geq 2\\ 2,& \text{if } n = 1 \\ 1, & \text{if } n = 0 \\ \end{cases} \] One of his friend pointed out that there is some error in the formula written by Chef so he added something in Chef's equat

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solution.cppC++17

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