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 C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include<iostream>
using namespace std;




int main()
{
	long long int N, K,  b, ans=0;
	cin >> N >> K;

	if (K == 0)
		ans = N * N;
	else for (b = K+1 ; b <= N; b++) {
		ans += (b - K)*(N / b);
		if (N / b * b + K <= N)
			ans += N - (N / b * b + K) + 1;

	}

	cout <<ans<< endl;

	return 0;
}