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 Kotlin (1.0.0) (judge verdict: Accepted)

fun main(args: Array<String>) {
    arc091d()
}

fun arc091d() {
    val (n, k) = readLine()!!.split(' ').map { it.toLong() }

    if (k==0L) return println(n*n)
    
    var answer = 0L

    for (b in k + 1..n) {
        answer += (n / b) * (b - k) + max((n % b) - (k - 1), 0)
    }

    println(answer)
}

private fun max(a: Long, b: Long) = Math.max(a, b)