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)

import sys
sys.setrecursionlimit(10 ** 7)

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

ans = 0
for n in range(N + 1):
    # 無理
    if n <= K:
        continue

    if K == 0:
        ans += N
        continue

    # 倍数分
    ans += (N // n) * (n - K)
    # あまり分
    if K <= (N % n):
        ans += (N % n) - K + 1


print(ans)