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