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 (GCC 5.4.1) (judge verdict: Wrong Answer)

/*
 AtCoder XXX 000
 */
 
#include <stdio.h>
 
int main(void){
  int n,k;
  int a,b;
  unsigned long long cnt;
  
  scanf("%d %d",&n,&k);
  
  cnt=0;
  for(a=k; a<=n; a++) for(b=k+1; b<=n; b++){
    //printf("(%d,%d)\n",a,b);
    if( a >= b )
    {
      if( a%b >= k ) cnt++;
    }
    else
    {
      if( a >= k ) cnt++;
    }
  }
  
  printf("%llu",cnt);
  
  return 0;
}