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)

#include <iostream>
using namespace std;

#define is_uruu main
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define ROF(i,a,b) for(int i=(a);i>(b);--i)
    
int is_uruu() {
	int N,K;
	long long count=0;
	cin >> N >> K;
	
	FOR(b,K+1,N+1){
		if((N%b)-K >=0){
			count += (b-K)*(N/b)+(N%b+1)-K;
		}
		if((N%b)-K < 0){
			count += (b-K)*(N/b);
		}
	}
	cout << count << endl;
    return 0;
}