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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
var dp = new Int32Array(18257);
dp[0] = 1;
for (var i = 1; i < 18257; i++)
	dp[i] = dp[i - 1] + 12 * i;

print(dp[readline() - 1]);