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 PyPy3 (2.4.0) (judge verdict: Accepted)

N, K = map(int, input().split())

ans = 0

if K == 0:
    print(N*N)
    exit()

for b in range(K+1, N+1):
    max_p = N // b
    max_q = N % b
    if max_q < K:
        max_p -= 1
        max_q = b - 1
    # print(b,max_p,max_q)
    ans += max_p * (b-K) + (max_q-K+1)

print(ans)