Star

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

inputFormat

Input

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

outputFormat

Output

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

Examples

Input

2

Output

13

样例

2

13

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