Pick’s formula

Pick's formula:$ $
Pick's formula: $\color{NavyBlue}S \color{Black}=$
Pick's formula:$ $
Pick's formula: $\color{NavyBlue}S \color{Black} = \color{ForestGreen}N_1 \color{Black}/2 + \color{BrickRed}N_2 \color{black} - 1$
Calculation of the area of a polygon
with vertices at the nodes of checkered paper.
Learn, how
Enter the area of the «simple» triangle.
A «simple» triangle — no grid nodes neither inside
nor on sides, except for vertices.
Statement. Any polygon with vertices
in grid nodes can be triangulated,
i.e. split into «simple»triangles.
Draw a non-self-intersecting polygon.
Unit of measure — squared parrot.
Please don't disturb.