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<stdlib.h>
#include<string.h>

int main(){
    int a, b, i;
    unsigned long int ttl = 0;
    scanf("%d %d", &a, &b);

    if(b == 0) ttl = a * a;

    for(i = 1; i <= a && b != 0; i++){
        if(i <= b) continue;
        else {
            ttl += (a / i) * (i - b);
            if(a % i >= b) ttl += (a % i - b + 1);
        }
    }

    printf("%lu\n", ttl);
    return 0;
}