#include <iostream>
using namespace std;

int main()
{
	int X, Y, L;
	cin >> X >> Y >> L;

	int turnCnt = 0;

	if (X != 0 || (X == 0 && Y < 0))
	{
		turnCnt++;
	}

	if (Y < 0)
	{
		turnCnt++;
	}

	int stepCnt = 0;
	stepCnt += 1 + (abs(X) - 1) / L;
	stepCnt += 1 + (abs(Y) - 1) / L;

	cout << turnCnt + stepCnt << endl;
}