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 (Clang 3.8.0) (judge verdict: Wrong Answer)

#include <stdio.h>
 
int main(){
  int n, k;
  scanf("%d %d", &n, &k);
  if (k == 0) {
    printf("%lld\n", (long long)(n * n));
    return 0;
  }
  
  long long ans = 0;
  for (int b = k+1; b <= n; ++b) {
    int h = b - k;
    int w = n / b;
    int rh = (n % b>= k) ? (n % b - k + 1) : 0;
    ans += h * w + rh;
  }
  printf("%lld\n", ans);
  return 0;
}