Sum of squares Cnk

Very easy

Execution time limit is 1 second

Runtime memory usage limit is 128 megabytes

Given a non-negative integer $n$ , find the sum of binomial coefficients

(C_{n}^{0})^{2} + (C_{n}^{1})^{2} + (C_{n}^{2})^{2} + ... + (C_{n}^{n})^{2}

Input

One non-negative integer $n (n \leq 30)$ .

Print the value of the sum.

Input #1

Answer #1

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