import math
a, b, x = map(int, input().split())
 
h = x / (a * a) #height 
if h > b / 2:
  shahen = 4 * (b - x/(a * a) * (b - x/(a * a))) + a * a
  sin = a / (math.sqrt(shahen))
  print(90 - math.degrees(math.asin(sin)))
elif h == b / 2:
  print(45.0000000000)
else:
  shahen = 4 * x * x + (a * a * a * a) * b * b
  sin = 2 * x / (math.sqrt(shahen))
  print(90 - math.degrees(math.asin(sin)))
