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 Scala (2.11.7) (judge verdict: Accepted)

object Main extends App {

  val In = io.StdIn.readLine()
  val A = In.split(" ")
  val N: Long = A(0).toLong
  val K: Long = A(1).toLong
  var sum: Long = 0

  if (K == 0) {
    sum = N * N
  } else {
    for (b <- K + 1 to N) {
      var p: Long = N / b
      val r: Long = N % b

      sum += p * (b - K)
      sum += (r - K + 1).max(0)
    }
  }

  print(sum)

}