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 rep(i,l,n) for(int i=l;i<n;i++)

int main(void){
    int N,K;
    long long count=0LL;
    cin>>N>>K;
    if(K==0){cout<<N*N<<endl;return 0;}
    int q,r;
    rep(b,K+1,N+1){
        q=N/b;
        count+=q*max(0,b-K)+max(0,N%b-K+1);
    }
    cout<<count<<endl;
    return 0;
}