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: Accepted)

N,K = gets.split.map(&:to_i)

puts (K+1..N).map{ |b|
  m1 = (N+1)/b
  n2 = (N % b < b-1) ? [N % b, K-1].max - K + 1 : 0
  #$stderr.puts "#{b}: #{m1} * #{(b-K)} = #{m1*(b-K)} #{n2}"
  m1*(b-K) + n2 + (K == 0 ? -1 : 0)
}.inject(:+)