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) {
        int init, N, K, i, j, result;
        result = 0;
        scanf("%d %d", &N, &K);
        if (K == 0)
                init = 1;
        else
                init = K;
        // K % X = K if X > K. mum = N - K
        //result += N - K;
        // Y % X = K.
        for (i = 1; i <= N; i++) {
                for (j = 1; j <= N; j++) {
                        if (i % j >= K) {
                                //printf("%d %d\n", i, j);
                                result += 1;
                        }
                }
        }
        printf("%d\n", result);

}