$/=$";($n,$s,$k)=<>;
$s-=$k*$n*($n-1)/2;
if($s>0){
	$d[$s]=1;
	for$i(0..$n-1){
		for$a(0..$s){
			for$b(0..$s/($n-$i)){
				$e[$a]+=$d[$a+$b*($n-$i)];
				$e[$a]%=1e9+7;
			}
		}
		@d=@e;@e=();
	}
}
print$d[0]+0;