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 (4.10.0) (judge verdict: Accepted)

Scanf.scanf "%d %d" (fun n k ->
    let rec loop b acc =
        if b > n then acc else
            let m = n / b in
            let r = n - m * b in
            let acc = acc + m * (b - k) + if k = 0 then max 0 (r - k) else max 0 (r - k + 1) in
            loop (b + 1) acc
    in
    loop (k + 1) 0 |> Printf.printf "%d\n"
)