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VK Cup 2012 Wild-card Round 1:

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A. Pentagonal numbers

time limit per test

3 secondsmemory limit per test

256 megabytesinput

standard inputoutput

standard outputPentagonal numbers are figurate numbers which can be calculated using the formula *p*_{n} = (3*n*^{2} - *n*) / 2 (always integer). You are given *n*; calculate *n*-th pentagonal number.

Input

The only line of input contains an integer *n* (1 ≤ *n* ≤ 100).

Output

Output the *n*-th pentagonal number.

Examples

Input

2

Output

5

Input

5

Output

35

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