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)

#include <stdio.h>
int main(){
    int N,K;
    scanf("%d %d",&N,&K);

    long total = 0;
    if (K == 0){
        total += N*N;
    }else{
        for (int b = K+1;b <= N;b++){
            int rn = N%b;
            int qn = (N-rn)/b;
            total += qn*(b-K);
            if (rn >= K) total += rn-K+1;
        }
    }

    printf("%ld\n",total);
}