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 Python (3.4.3) (judge verdict: Accepted)

n, k = map(int, input().split())
ans = 0
i = 0
if k == 0:
    ans = n ** 2
else:
    while i <= n:
        if i >= k:
            ans += n // (i + 1) * (i - k + 1)
        if k <= n % (i + 1) < n:
            ans += n % (i + 1) - (k - 1)
        i += 1
print(ans)