<?php
$x = trim(fgets(STDIN));
$y = trim(fgets(STDIN));
$l = trim(fgets(STDIN));
if($y >= 0){
if($x == 0){
echo ceil($y / $l)."\n";
}else{
echo ceil(abs($x) / $l) + ceil($y / $l) + 1 ."\n";
}
}else{
echo ceil(abs($x) / $l) + ceil(abs($y) / $l) + 2 ."\n";
}