import java.util.Scanner;

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

		int x = sc.nextInt(), y = sc.nextInt(), r = sc.nextInt(), z = 0, w;
		if(x < 0){x *= -1;}
		if(y < 0){y *= -1;}
		while(z*z*2 <= r*r){z++;}
		w = z;
		if(z*(z-1)*2 >= r*r){w--;}
		System.out.println(x+y+z+w);
	}
}