python - Reducing a variable on iteration of a loop -

i created following code works out how many rushes heffa lump needs hill. next stage have make every time heffalump rushes hill, becomes tired , rush_height_gain reducded 5% each time.

def num_rushes(slope_height, rush_height_gain, back_sliding):     """herbert heffalump"""     current_height = 0     rushes = 0     while current_height < slope_height:         rushes += 1         current_height += rush_height_gain         if current_height >= slope_height:             break         current_height -= back_sliding      return rushes  ans = num_rushes(100, 15, 7) print(ans)  

this should = 19

i understand part of problem height gain value becomes less slide added line break code when happens. however, cannot life of figure out how make height gain reduced 5% each time