import math
L = int(input())
W = int(input())
A = int(input())

hall_area = (L * 100) * (W * 100) # multiply x 100 to convert to sm
wardrobe = (A * 100) * (A * 100)
bench = hall_area / 10
free_space = hall_area - wardrobe - bench
dancers = free_space / (40 + 7000) # 40 space needed for single dancer , 7000 space when moving
print(math.floor(dancers))