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>

int main(void){
    int a, b;
    int i, j;
    int count = 0;

    scanf("%d %d", &a, &b);
    if(b){
        for(i=a-b;i>0;i--){
            count += i;
        }
        for(i=b+1;i<=a;i++){
            for(j=i+1;j<=a;j++){
                if(j%i>=b){
                    count += 1;
                }
            }
        }
    }else{
        count = a * a;
    }
    printf("%d\n", count);
    return 0;
}