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: Runtime Error)

#include <stdio.h>

int main(){
  int n, k;
  scanf("%d %d", &n, &k);
  if (k == 0) {
    printf("%d\n", n * n);
  }
  
  int ans = (n - k + 1) * (n - k) / 2;
  for (int a = 2; a <= n; a++) {
      for (int b = k; b < a; b++) {
        ans += a % b >= k;
      }
  }
  printf("%d\n", ans);
  return 0;
}