($n,$s,$w)=<>=~/\d+/g;
@a=<>=~/\d+/g;
($w)=splice@a,$w,1;
@a=sort{$b<=>$a}@a;
@b=map{50*$s+int(50*$s/(0.8+0.2*$_))}1..@a;

$i=$#b;
$c=$d=1;
for(@a){
	while($i>=0 && $b[$i]+$_<=$b[0]+$w){
		--$i;
	}
	++$j;
	$c*=@b-$i-$j;
	$d*=$j;
}
print $c/$d;