#include<iostream>
#include<cmath>
using namespace std;

int main()
{
    int x, y, l;
    int time = 0;

    cin >> x >> y >> l;
    if(y < 0){
        time += 2;
    }
    time += ceil(fabs(y)/l);
    if(x != 0) time++;
    time += ceil(fabs(x)/l);
    cout << time << endl;

    return 0;
}