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: Accepted)

#include<iostream>
#include<vector>
#include<algorithm>
#include<cctype>
#include<utility>
#include<string>

#define REP(n) for(int i = 0;i < n;i++)
#define LLREP(n) for(long long int  i = 0;i < n;i++)
typedef long long int ll;
using namespace std;
#define MAX_A 1000000007

int main(){

    ll n,k,ans = 0;
    cin >> n >> k;


    for(ll b = 1;b <= n;b++){

        ll dis = n/b;
        ll mod = n%b;
        ans += dis*max(0LL,b-k)+max(0LL,mod-k+1);
    }
    if(k == 0){
        ans-=n;
    }
    cout << ans << endl;






    return 0;
}