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 Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.util.Scanner;

class Main {
    public static void main(String[] args) {
        long n = 0, k = 0;
        boolean flag = false;
        Scanner sc = new Scanner(System.in);
        if (k == 0) {
            System.out.println(n * n);
            sc.close();
            flag = true;
        }
        if (flag) {
            long res = 0;
            for (long i = k + 1; i <= n; i++) {
                res += n / i * (i - k);
                res += (n % i - k + 1 > 0) ? n % i - k + 1 : 0;
            }
            System.out.println(res);
            sc.close();
        }
    }
}