a, b, x = gets.chomp.split.map(&:to_f)

if x > a*a*b/2
  min, max = 0, Math.atan(b/a)
  while (max - min) * 180 / Math::PI > 10**-7
    mean = (max + min) / 2
    if x < a*a*b - a*a*a*Math.tan(mean)/2
      min = mean
    else
      max = mean
    end
  end
else
  min, max = Math.atan(b/a), Math::PI/2
  while (max - min) * 180 / Math::PI > 10**-7
    mean = (max + min) / 2
    if x < a*b*b/(2*Math.tan(mean))
      min = mean
    else
      max = mean
    end
  end
end


puts((max + min) * 90 / Math::PI)