A. Alex and a Rhombustime limit per test1 secondmemory limit per test256 megabytesinputstandard inputoutputstandard outputWhile playing with geometric figures Alex has accidentally invented a concept of a n-th order rhombus in a cell grid.A 1-st order rhombus is just a square 1 \times 1 (i.e just a cell).A n-th order rhombus for all n \geq 2 one obtains from a n-1-th order rhombus adding all cells which have a common side with it to it (look at the picture to understand it better).  Alex asks you to compute the number of cells in a n-th order rhombus.InputThe first and only input line contains integer n (1 \leq n \leq 100) — order of a rhombus whose numbers of cells should be computed.OutputPrint exactly one integer — the number of cells in a n-th order rhombus.ExamplesInput
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1Input
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5Input
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13NoteImages of rhombus corresponding to the examples are given in the statement.
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