When submitting a solution in C++, please select either C++14 (GCC 6-32) or C++17 (GCC 7-32) as your compiler. ×

B. Star
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output
Input

The input contains a single integer a (1 ≤ a ≤ 18257).

Output

Print a single integer output (1 ≤ output ≤ 2·109).

Examples
Input
2
Output
13