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.chomp.split(" ").map(&:to_i)

ans = 0
(K+1).upto(N){|i|
  ans += N/i * (i-K)
  if K == 0 then
    ans += (N % i) - K if N % i > 0 && (N % i) - K > 0
  else
    ans += (N % i) - K + 1 if N % i > 0 && (N % i) - K >= 0
  end
}

puts ans