sub min{$_[0]<$_[1]?$_[0]:$_[1]}
sub max{$_[0]>$_[1]?$_[0]:$_[1]}
($d,$i,$h,$j)=<>;
exit!print $i<$h&&$j<$h||$i>$h&&$j>$h?0:-1 if $d==0;
$n=min($i,$j)==0?1e11:max(0,int(($h-min($i,$j)+$d)/$d));
$o=$h==0?1e11:max(0,int(($i-$h+$d)/$d));
$p=$h==0?1e11:max(0,int(($j-$h+$d)/$d));
$h1=max(0,$h-$d*$n);
$i1=max(0,$i-$d*$o);
$j1=max(0,$j-$d*$p);
if($i==$j){
    if($i==0){
	$n=1e11;
    }else{
	++$n;
	if($i-$d<=$h){
	    ++$n;
	    if(max(0,$h-$d)==max(0,$i-$d)){
		$n=1e11;
	    }
	}
    }
}
$o=$i1==0?1e11:$o+1 if $i1==$j1;
$n=min($n,$o+$p);
$n=-1 if $n>=1e11;
print$n