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)

#pragma once
#include <stdio.h>
#include <string>
#include <iostream>
#include <queue>
#include <algorithm>
#include <sstream>

using namespace std;

long long result, n,m,k;

long long total[2] = {};

long long a[100000] = {};

int main() {

	cin >> n >> k;
	
	result =0;

	for (int i = k+1; i <= n; i++) {
		result += (n / i)*(i - k);
		if (n%i >= k) {
			if (k != 0) {
				result += (n%i) - k + 1;
			}
			if (k == 0) {
				result += (n%i) - k;
			}

		}

	}


	cout << result << endl;

return 0;
}