import java.util.Scanner;


public class Main_yukicoder172 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int x = Math.abs(sc.nextInt());
        int y = Math.abs(sc.nextInt());
        int r = sc.nextInt();
        int min = Math.min(x, y);
        int tmp = (int)Math.ceil((Math.sqrt(2.0) * min + r) * Math.sqrt(2.0));
        System.out.println(Math.abs(x - y) + tmp);
        
        sc.close();
    }
}