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 Go (1.6) (judge verdict: Time Limit Exceeded)

package main

import "fmt"

var N, K int

func main() {
	fmt.Scanf("%d %d", &N, &K)

	if K == 0 {
		fmt.Println(N * N)
		return
	}

	// (a, b)
	// 0 < a,b <= N
	// K <= a%b < N
	// K < a <= N
	// K < b <= N

	ans := 0
	for c := K; c < N; c++ {
		for b := c + 1; b <= N; b++ {
			ans += (N-c)/b + 1
		}
	}

	fmt.Println(ans)
}