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 (3.8.2) (judge verdict: Accepted)

n, k = map(int, input().split())
ans = 0

if k == 0:
    print(n*n)
    exit()

# mod b ということは、あまり0~b-1が n // b回つづく
for b in range(k, n+1):
    x = n // b
    y = n % b
    ans += (b-k) * x
    if y >= k:
        ans += y + 1 - k
print(ans)