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)

int main(){
  int n, k, ans=0;

  scanf("%d\t%d", &n, &k);

  // a<b : (n-k)+(n-k-1)+...+2+1
  for(int i=1; i<=n-k; i++){
    ans += i;
  }
  //printf("%d\n", ans);

  // a>b : a>3, b>=k+1>=2, bはaの約数でない
  for(int i=k+2; i<=n; i++){
    for(int j=2; j<i; j++){
      if(i%j>=k){
	ans++;
	//printf("%d,%d\n", i,j);
      }
    }
  }


  
  /*
  for(int i=1; i<=n; i++){
    for(int j=1; j<=n; j++){
      if(i%j>=k){
	ans++;
	if(j<i)printf("a=%d,b=%d\n", i, j);
      }
      
    }
    }*/
  
  printf("%d\n", ans);

  return 0;
}