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: Time Limit Exceeded)

#include<bits/stdc++.h>
using namespace std;
long long ans,n,k;
inline int read()
{
	int num=0,f=1;
	char c=getchar();
	for(;c<'0'||c>'9';c=getchar())
	if(c=='-')f=-1;
	for(;c>='0'&&c<='9';c=getchar())
	num=(num<<1)+(num<<3)+c-48;
	return num*f;
}
void init()
{
	n=read();k=read();
}
void work()
{
	if(k==0)
	{
		cout<<n*n;
		exit(0);
	}
	for(int i=k;i<=n;++i)
	for(int j=k;j<=n;++j)
	{
		if(i%j>=k)ans++;
	}
	cout<<ans;
}
int main()
{
	init();
	work();
	return 0;
}