<?php
$X = trim(fgets(STDIN));
$Y = trim(fgets(STDIN));
$L = trim(fgets(STDIN));
$ans = 0;
if($Y >= 0) {
  $ans += (intdiv($Y + $L - 1, $L));
  $ans += (intdiv(abs($X) + $L - 1, $L));
  if($X != 0) $ans += 1;
} else if($Y < 0) {
  $ans += (intdiv(abs($Y) + $L - 1, $L) + 2);
  $ans += (intdiv(abs($X) + $L - 1, $L));
}
print($ans);
?>