Excel count number of cells in column with "an" until next cell is non"an"

Excel count number of cells in column with "an" until next cell is non"an"

I would like to count the number of cells in column with "an", where the
counting starts at a given row and counts go down to count the number of
cells with "an" until a non-"an" cell is found?
For example Column A : opp an an an an opp
I would like to calculate how many cell with "an" until the next non an
cell. For this example answer will be 4.
Another example Column B :an an opp an an an
The answer will be 2.