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: Accepted)

import java.util.Scanner;

public class Main {

	public static void main(String args[]) {
		Scanner sc = new Scanner(System.in);
		long n = sc.nextInt();
		long k = sc.nextInt();

		if(k == 0) {
			System.out.println(n * n);
			System.exit(0);
		}

		if(n == 1) {
			System.out.println("0");
			System.exit(0);
		}

		long ans = 0;
		for(long i = 1;i <= n;i++) {
			long a = n / i;
			long b = n % i;

			if(i >= k) {
				ans += (i - k) * a;
			}
			if(b - k >= 0 ) {
				ans += b - k + 1;
			}
		}
		System.out.println(ans);
	}
}