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)


def Z(): return int(input())
def ZZ(): return [int(_) for _ in input().split()]

def main():
    N, K = ZZ()
    output = 0
    for b in range(1, N+1):
        output += N//b * max(0, b-K)
        output += max(0, N%b-K+1)
        if K == 0: output -= 1
    print(output)

    return

if __name__ == '__main__':
    main()