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 (Clang 3.8.0) (judge verdict: Accepted)

#include<stdio.h>
int max(int a,int b){return a>b?a:b;}
int main()
{
	long long n,k,sum=0;
	scanf("%lld%lld",&n,&k);
	if(k==0)sum=n*n;
	else for(int i=k+1;i<=n;i++)sum+=(n/i)*(i-k)+max(0,(int)n%i-(int)k+1);
	printf("%lld\n",sum);
}