Task

You have a rectangular white board with some black cells. The black cells create a connected black figure, i.e. it is possible to get from any black cell to any other one through connected adjacent (sharing a common side) black cells.

Find the perimeter of the black figure assuming that a single cell has unit length.

Example

For

matrix = [[false, true,  true ],
          [true,  true,  false],
          [true,  false, false]]```
the output should be `12`.

 ![](https://codefightsuserpics.s3.amazonaws.com/tasks/polygonPerimeter/img/example1.png?_tm=1474901184061)

 For

matrix = [[true, true, true], [true, false, true], [true, true, true]]``` the output should be 16.

Input/Output

• [input] 2D boolean array matrix

  A matrix of booleans representing the rectangular board where true means a black cell and false means a white one.

  Constraints:

  2 ≤ matrix.length ≤ 10,

  2 ≤ matrix[0].length ≤ 10.

• [output] an integer