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: Time Limit Exceeded)

#include<stdio.h>
int main(void)
{
  long count=0, max,mod,a,b;
  scanf("%ld%ld",&max,&mod);
  b=mod;
  if(mod!=0)
  {
    while(b<=max)
    {
      count=count+ (max/b)*(b-mod);
      a=(max/b)*b;
      while(a<=max)
      {
        if(a%b>=mod) count++;
        a++;
      }
      b++;
    }
  }
  else count=max*max;
  printf("%ld",count);
  return 0;
}