#include <bits/stdc++.h>
using namespace std;
 
int main(){
   int X,Y,L;
   cin>>X>>Y>>L;
   int count=0;
   if(Y>=0){
       int a=Y;
       while(a>0){
           a-=L;
           count++;
       }
       if(X!=0){
           count++;
       }
       int b=abs(X);
       while(b>0){
           b-=L;
           count++;
       }
   }
   else{
       count+=2;
       int a=abs(Y);
       int b=abs(X);
       while(a>0){
           a-=L;
           count++;
       }
       while(b>0){
           b-=L;
           count++;
       }
   }
   cout<<count<<endl;
}