Sum of squares Cnk#11271
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Sum of squares Cnk

1 second
128 megabytes
Very easy

Given a non-negative integer , 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 \le 30).

Output

Print the value of the sum.

Examples

Example 1

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