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: Accepted)

fun main(arr: Array<String>) {
    val (n,k) = readLine()!!.split(" ").map { it.toInt() }
    var ans = 0L
    for(i in (k+1..n)) {
        val min = 0
        var max = (n / i)
        if(max*i+k > n) {
            max--
        }
        ans += (max-min)*(i-k)
        ans += Math.min(i*(max+1)-1, n) - (i*max+k)+1
    }
    if(k == 0) {
        ans -= n
    }
    println(ans)
}