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 Ruby (2.3.3) (judge verdict: Wrong Answer)

io = STDIN
n,k=io.gets.split.map(&:to_i)
if k==0
  puts n*n
else
  cnt1 = (1..(n-k)).inject(:+)
  cnt2=0
  (k..n).each do |a|
    (k...a).each do |b|
      cnt2 += 1 if a%b>=k
    end
  end
  p [cnt1,cnt2]
  puts cnt1+cnt2
end