<?php
    $x = trim(fgets(STDIN));
    $y = trim(fgets(STDIN));
    $l = trim(fgets(STDIN));
    
    $count = 0;
    
    //南北の方向
    if($y > 0){
        $count = ceil(abs($y) / $l);
        //echo $count."\n";
    }elseif($y < 0){
        $count = 2 + ceil(abs($y) / $l);
        //echo $count."\n";
    }
    
    //東西
    if($x != 0){
    $count = $count + 1 + ceil(abs($x) / $l);  
    }
    
    echo $count;
?>