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: Wrong Answer)

using namespace std;

#include <iostream>
#include <vector>
#include <cmath>

typedef long long ll;


int main() {
  int N, K;
  cin >> N >> K;
  int ans = 0;
  
  for (int b = 1; b <= N; b++) {
    int can_divide = N / b;
    int res = N % b;
    ans += max(0, can_divide * (b - K));
    if (res >= K) {
      ans += max(0, res - K + 1);
    }
    
  }
  if (K == 0) ans -= N;
  cout << ans << endl;
  return 0;
}