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.io.*;
import java.util.*;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		StringTokenizer st = new StringTokenizer(scan.nextLine());
		long startTime = System.currentTimeMillis();
		scan.close();
		int N = Integer.parseInt(st.nextToken());
		int K = Integer.parseInt(st.nextToken());
		if(K==0) {
			System.out.println(N*N);
			System.exit(0);
		}
		long count = 0;
		for(int b=K+1; b<N+1; b++) {
			long n = (N+1)/b;
			long d = 0;	
			d+= (b-K) * n;
			long L = K + b * n;
			long R = N;
			if(L <= R) {
				d+= R - L + 1;
			}
			count+=d;
		}
		System.out.println(count);
		//System.out.println("Done in: " + (System.currentTimeMillis()-startTime) + " ms");
	}
}