($n,$s,$w)=<>=~/\d+/g;
@a=<>=~/\d+/g;
($w)=splice@a,$w,1;
@a=sort{$b<=>$a}@a;
@b=map{50*$s+int(250*$s/(4+$_))}1..@a;

$r=0;
$i=$#b;
eval{
for(@a){
	while($i>=0 && $b[$i]+$_<=$b[0]+$w){
		--$i;
	}
	++$j;
	$c+=log(@b-$i-$j)-log$j;
}
$r=exp$c;
};
print $r;