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.*;

public class Main {
	
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		
		int N = in.nextInt();
		int K = in.nextInt();
		
		long ans = 0;
		if (K == 0) {
			ans = (long) N * (long) N;
		} else {
			for (int b = 1; b <= N; b++) {
				if (b <= K) {
					continue;
				}
				ans += (b - K) * (N / b);
				if (N % b >= K) {
					ans += N % b - K + 1;
				}
			}
		}
		
		System.out.println(ans);
	}
}