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 Rust (1.15.1) (judge verdict: Wrong Answer)

use std::io::stdin;

fn main() {
	let (n, k) = get_ints();

	let mut counter = 0;

	for a in k..(n+1) {
		for b in 1..(n+1) {
			if a % b >= k {
				counter += 1;
			}
		}
	}

	println!("{}", counter)
}

fn get_ints() -> (i32,i32) {
	let mut s = String::new();
	stdin().read_line(&mut s)
		.map_err(|err|{
			println!("{:?}",err);
		})
		.unwrap();
	let v: Vec<&str> = s.split_whitespace().collect();
	let int1: i32 = v[0].parse().unwrap_or(0);
	let int2: i32 = v[1].parse().unwrap_or(0);
	(int1, int2)
}