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 sc = new java.util.Scanner(System.in)
  val N, K = sc.nextLong

  var sum :Long = 0
  if (K == 0) {
    println(N * N)
    sys.exit
  }

  for (b <- K + 1 to N) {
    val x = N % b
    if (x >= K) {
      sum += (b - K) * (N / b) + x + 1 - K
    } else {
      sum += (b - K) * (N / b)
    }
  }

  println(sum)
}