def get_int
  gets.chop.to_i
end

def get_ints
  gets.chop.split.map(&:to_i)
end

def get_double
  gets.chop.to_f
end

def get_str
  gets.chop
end

def get_strs
  gets.chop.split
end

def main
  s = get_strs
  a = s[0].to_i
  b = s[1].to_i
  x = s[2].to_f
  x = x / a
  if x >= (a * b / 2.0)
    tan_z = 2.0 * (a * b - x) / (a * a * 1.0)
  else
    tan_z = b * b / (2.0 * x)
  end
  rad_z = Math.atan(tan_z)
  z = rad_z * 180.0 / Math::PI
  puts z
end

if __FILE__ == $0
  main
end