There exists an infinitely large two-dimensional grid of uncolored unit cells. You are given a positive integer?n, indicating that you must do the following routine for?n?minutes:

• At the first minute, color?any?arbitrary unit cell blue.

• Every minute thereafter, color blue?every?uncolored cell that touches a blue cell.

Below is a pictorial representation of the state of the grid after minutes 1, 2, and 3.

Return?the number of?colored cells?at the end of?n?minutes.

?

Example 1:

Input: n = 1

Output: 1

Explanation: After 1 minute, there is only 1 blue cell, so we return 1.

Example 2:

Input: n = 2

Output: 5

Explanation: After 2 minutes, there are 4 colored cells on the boundary and 1 in the center, so we return 5.

?

Constraints:

• 1 <= n <= 105

總結(jié)出規(guī)律，題目就好做了；2*n2-2*n+1;

Runtime:?0 ms, faster than?100.00%?of?Java?online submissions for?Count Total Number of Colored Cells.

Memory Usage:?39.5 MB, less than?100.00%?of?Java?online submissions for?Count Total Number of Colored Cells.