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: Time Limit Exceeded)

#include <algorithm>
#include <bitset>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <ctime>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <utility>
#include <vector>

using namespace std;

typedef long long ll;
typedef vector <int> vi;
typedef vector < vector <int> > vvi;
const int HUGEI = 2147483647;  // (1 << 31) - 1
const ll HUGEL = 9223372036854775807;  // (1 << 63) - 1
const string ABC = "abcdefghijklmnopqrstuvwxyz";

int main(void) {
    int n, k, a, b, res;
    cin >> n >> k;
    res = 0;
    for (a = 1; a <= n; a++) {
        for (b = 1; b <= n; b++) {
            if (a % b >= k) res++;
        }
    }
    cout << res << endl;
    return 0;
}