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>
#include <string>
using namespace std;

int main() {
	int N, K;
	int ans = 0;

	cin >> N >> K;

	if (K == 0) {
		cout << N*N << endl;
		return 0;
	}

	ans += (N - K)*(N - K + 1) / 2;

	for (int i = K+1; i < N; i++) {
		for (int j = i + 1; j < N + 1; j++) {
			if (j%i >= K) {
				ans++;
			}
		}
	}

	cout << ans << endl;

	return 0;
}