Increasing and decreasing depending of column C

Hi,
I have the next problem:
I have two columns A and B. In the first row we have value 1 in both columns, and this will be increased or decreased in function of what is in column C.
In column C we have a list of elements in a random order. This elements are G1, G2, or G3.
If the element in Column C is G1 in the next row the value of column A will increase, and the value of column B will decrease. If the value of Column C is G2, will happen the opposite, Column A will decrease, and column B will increase. If the value of Column C is G3 both column A and B will decrease.
The value of both columns could increase without limit, but just decrease till 1.
For example,

4 8 G2

Because in column C we have G2 will increase column B, and decrease column A:

3 9

But at the start, we have this in columns A and B, and could have this in column C:

1 1 G1

Then we will have in the next row

2 1

The column B could not decrease, because the minimum limit is “1".

If we have this:

3 5 G3

both decrease:

2 4

I attached an example worksheet to make this more clear.

Thank you very much for your help.

Caldera55