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 <bits/stdc++.h>
using namespace std;

#define llong long long
#define inf 999999999
#define mp make_pair
#define pb push_back
#define fn fill_n
typedef pair<int, int> P;
typedef pair<P, int> PP;
typedef pair<PP, int> PPP;
typedef struct data{
	int now;
	int cost;
}data;
int nh[4] = {1, 0, -1, 0};
int nw[4] = {0, 1, 0, -1};





int main(){
	int n, k;
	llong int ans = 0;
	cin >> n >> k;
	for(int i = 1; i <= n; i++){
		ans += n/i*max(0, i - k) + max(0, n%i - k + 1);
	}
	if(k == 0) ans -= n - k;
	cout << ans << endl;
	return 0;
}