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)

#include<stdio.h>
#include<math.h>
int main()
{
    int n,k,i,j,count,p,r;
    long long sum=0;
    int max(int a,int b);
    scanf("%d%d",&n,&k);
    for(i=k+1;i<=n;i++)
    {
        r=n%i;
        p=n/i;
        sum+=p*max(0,i-k);//前半段;
        sum+=max(0,r-k+1);//后半段;
    }
    printf("%lld\n",sum);
    return 0;
}
int max(int a,int b)
{
    if(a>b) return 0;
    else return b;
}