#include<iostream>
using namespace std;
int main() {
	int X, Y, K;
	int x = 0, y = 0, angle = 0, turn = 0;
	cin >> X >> Y >> K;
	while (Y > y) {
		turn++;
		if (y + K > Y) {
			y = Y;
		}
		else {
			y += K;
		}
	}
	while (X != x) {
		if (angle == 0) {
			turn++;
			if (X < x) {
				X = X * -1;
				angle = 3;
			}
			else {
				angle = 1;
			}
		}
		if (x + K > X) {
			x = X;
		}
		else {
			x += K;
		}
		turn++;
	}
	while (Y != y) {
		if (angle != 2) {
			if (angle == 0) {
				turn++;
				angle = 1;
			}
			turn++;
			Y = Y * -1;
			angle = 2;
		}
		if (y + K > Y) {
			y = Y;
		}
		else {
			y += K;
		}
		turn++;
	}
	cout << turn << endl;
}