import math
a,b,x = map(int, input().split())

def xx(y):
  aHeight = a*math.sin(y)
  bHeight = b*math.sin(0.5*math.pi-y)
  if aHeight < bHeight:
    menseki = 0.5*a*b + (bHeight/aHeight*a-b)*math.sin(0.5*math.pi-y)*(a/math.cos(y))
  else:
    aD = bHeight/math.sin(y)
    menseki = 0.5*aD*b
  return menseki

minY = 0
maxY = 0.5*math.pi
while True:
  menseki = xx((minY+maxY)/2)
  if abs(x/a - menseki) < 0.1:
    print((minY+maxY)/2 * (180/math.pi))
    break
  elif menseki < x/a:
    maxY = (minY+maxY)/2
  else:
    minY = (minY+maxY)/2