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 <fstream>
#include <vector>
#include <algorithm>

using namespace std;
int main()
{
#ifdef LOCAL
    std::ifstream in("input.txt");
    std::cin.rdbuf(in.rdbuf());
#endif
    int N, K;
    cin >> N >> K;

    int count = 0;
    for(int b=1;b<=N;b++){
        int p = N/b;
        int r = N-p*b;

        count += p*max(0,b-K) + max(0, r-K+1);
        if(K == 0){
            count--;
        }
    }

    cout << count << endl;

    return 0;
}