import java.util.*;

public class Run {
    final static double s = Math.sin(Math.PI/4) * 2;
    public static void main (String arg[]) {
        Scanner scan = new Scanner(System.in);
        int x = Math.abs(scan.nextInt());
        int y = Math.abs(scan.nextInt());
        int r = scan.nextInt();
        double m = Math.ceil(x + y + r * s);

        System.out.println(m);
    }
}