#include<iostream>
#include<cmath>

using namespace std;

int main(){
  int x,y,l;
  cin >> x >> y >> l;
  int num_x,num_y,num_turn=2;
  if(y>=0){
    if(x==0){
      num_turn=0;
    }else{
      num_turn=1;
    }
  }

  x=abs(x);
  y=abs(y);
  while(x>0){
      x-=l;
      num_x++;
  }
  while(y>0){
      y-=l;
      num_y++;
  }
  cout << num_x + num_y + num_turn << endl;
  return 0;
}