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 (1.3.71) (judge verdict: Wrong Answer)

//

fun main() {
    arc091b()
}

fun arc091b() {
    val (n, k) = readLine()!!.split(" ").map { it.toInt() }
    if (k == 0) {
        println(n * n)
        return
    }
    var count = 0L
    for (b in k + 1 .. n) {
        val i = b - k
        val cycle = (n - k) / b
        count += cycle * i + i
        val over = cycle * b + k + i - 1
        if (over > n) {
            count -= (over - n)
        }
    }
    println(count)
}