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>) {
    val (N, K) = listOfLong()
    if (K == 0L) {
        println(N * N)
        return
    }
    var ans = 0L
    for (b in K + 1..N) {
        val p = N / b
        val r = N % b
        val k = Math.max(b - K, 0) * p + Math.max(r - K + 1, 0)
        ans += k
    }
    println(ans)
}

fun next() = readLine()!!
fun nextInt() = next().toInt()
fun nextLong() = next().toLong()
fun listOfString() = next().split(" ")
fun listOfInt(d: Int = 0) = listOfString().map { it.toInt() + d }
fun listOfLong(d: Long = 0) = listOfString().map { it.toLong() + d }