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 JavaScript (node.js v5.12) (judge verdict: Accepted)

function Main(input) {
	input = input.split(" ").map(a => parseInt(a));
	var N = input[0];
	var K = input[1];
	
	var ans = 0;
	if(K === 0) ans = N * N;
	else
	for(var b = K + 1; b <= N; b++){
		var t = Math.floor(N / b);
		ans += (b - K) * t;
		ans += Math.max((N - t * b) - K + 1, 0);
	}
	
	console.log(ans);
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));