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 = [int(c) for c in input().split()]

if N < K:
    print(0)
elif K == 0:
    print(N**2)
else:
    cnt = 0
    b_min = K+1 if K > 0 else 1
    for b in range(b_min, N+1):
        #print((N//b) * max(0, b-K) + max(0, (N%b)-K+1))
        cnt += (N//b) * (b-K) + max(0, N%b-K+1)

    print(cnt)