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>
#include <stdlib.h>
#include <math.h>
#include <time.h>

int main(){

    int i, j;
    char dammy;

    int N, K;
    scanf("%d %d", &N, &K);
    int a, b;

    unsigned long long count = 0;

    for (a = K; a < N+1; a++){
        for (b = K+1; b < N+1; b++)
        {
            if(a>b){
                if (a % b >= K)
                {
                    count++;
                    //printf("%d %d\n", a, b);
                }
            }else if(a<b){
                if(a>=K){
                    count++;
                }
            }
            
            
        }
    }
    
    printf("%llu", count);

    return 0;
}



int max(int a, int b){
    if(a > b){
        return a;
    }else{
        return b;
    }
}