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: Wrong Answer)

/*===============================================================
*  Filename: E.cpp
*  Author: zhuyutian
*  Date: 2018.04.16
================================================================*/
#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
const int maxn = 100005;

int n,K;

int main()
{
    //freopen("E.in","r",stdin);
    //freopen("E.out","w",stdout);
    scanf("%d%d",&n,&K);
	ll ans = 0;
	if(K == 0) ans = 1ll * n * n;
	for(int i = K; i <= n && K; i++){
		ans += n - i;
		for(int j = i; j <= n; j += i){
			if(j + i <= n) ans += i - K;
			else if(j + K <= n) ans += n - j - K + 1;
		}
	}
	printf("%I64d\n",ans);
	return 0;
}