#! ruby
# yukicoder My Practice
# author: Leonardone @ NEETSDKASU

x, y, r = gets.split.map(&:to_f)

len = x.abs + y.abs + 2.0 * r * (2.0 ** 0.5) / 2.0

if len.ceil == len.floor
	puts len.ceil.next
else
	puts len.ceil
end