Given is a positive integer N. How many tuples (A,B,C) of positive integers satisfy A \times B + C = N?

Constraints

* 2 \leq N \leq 10^6
* All values in input are integers.

Input

Input is given from Standard Input in the following format:


N


Output

Print the answer.

Examples

Input

3


Output

3


Input

100


Output

473


Input

1000000


Output

13969985
// C - A x B + C
#include <bits/stdc++.h>
using namespace std;

int main(){
	int n; cin>>n; --n;
	int c = 0;
	for(int x=1; x*x<=n; ++x) c += (n / x - x) * 2 + 1;
	cout<< c <<endl;
}
