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 C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<n;i++)
#define int long long
#define ll long long
#define INF LLONG_MAX/3
#define eps LDBL_EPSILON
#define moder 1000000007
#define pie 3.141592653589793238462643383279
#define P std::pair<int,int>
#define prique priority_queue<int,vector<int>,greater<int>>
using namespace std;
int n,k,ans;
signed main(){
	cin>>n>>k;
	for(int i=k+1;i<=n;i++){
		ans+=n-(n/i*k+min(n%i,max(k-1,(ll)0)));
	}
	cout<<ans<<endl;
    return 0;
}