Problem:
Score : 400 points

Problem Statement

Takahashi had a pair of two positive integers not exceeding N, (a,b), which he has forgotten.
He remembers that the remainder of a divided by b was greater than or equal to K.
Find the number of possible pairs that he may have had.

Constraints

1 \leq N \leq 10^5

0 \leq K \leq N-1

All input values are integers.

Input

Input is given from Standard Input in the following format:

N K

Output

Print the number of possible pairs that he may have had.

Sample Input 1

5 2

Sample Output 1

7

There are seven possible pairs: (2,3),(5,3),(2,4),(3,4),(2,5),(3,5) and (4,5).

Sample Input 2

10 0

Sample Output 2

100

Sample Input 3

31415 9265

Sample Output 3

287927211

Solution in PHP7 (7.0.15) (judge verdict: Accepted)

<?php
fscanf(STDIN, "%d %d", $n, $k);

if ($k === 0) {
	echo $n**2, "\n";
	return;
}

$minB = $k + 1;
$count = 0;
for ($b = $minB; $b <= $n; $b++) {
	$m = 0;
	$countA = 0;
	while ($m * $b <= $n) {
		if (($m + 1) * $b <= $n) {
			$countA += $b - $k;
			$m++;
			continue;
		}
		if ($m * $b + $k > $n) {
			$m++;
			continue;
		}

		$plus = $n - ($m * $b + $k) + 1;
		$countA += $plus;
		$m++;
	}
	$count += $countA;
}
echo $count, "\n";