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 OCaml (4.02.3) (judge verdict: Accepted)

let () = Printf.printf "%d\n" @@ Scanf.scanf "%d %d" (fun n k ->
  Array.init n (( + ) 1)
  |> Array.map (fun b ->
      max 0 (b - k) * (n / b)
    + min (n mod b) (max 0 (n mod b - k + 1)))
  |> Array.fold_left ( + ) 0)