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 Lua (5.3.2) (judge verdict: Accepted)

local n, k = io.read("*n", "*n")
local cnt = 0
local mm = math.max
for b = k + 1, n do
  cnt = cnt + (n // b) * (b - k)
  local rem = n % b
  if(0 < rem) then
    if(k == 0) then cnt = cnt + rem
    else cnt = cnt + mm(0, rem - k + 1)
    end
  end
end
print(cnt)