Problem:
Score : 300 points

Problem Statement

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.

Sample Input 1

3

Sample Output 1

3

There are 3 tuples of integers that satisfy A \times B + C = 3: (A, B, C) = (1, 1, 2), (1, 2, 1), (2, 1, 1).

Sample Input 2

100

Sample Output 2

473

Sample Input 3

1000000

Sample Output 3

13969985

Solution in C++ (GCC 9.2.1) (judge verdict: Accepted)

//Coded by Abhijay Mitra
#include <iostream>
#include <stdlib.h>
#include <algorithm>
#include <cstdio>
#include <numeric>
#include <cstring>
#include <numeric>
#include <vector>
#include <iterator> 
#include <map>
#include <set>
#include <climits>
#include <queue>
#include <cmath>
#include <stack>
#include <cctype>
#include <bitset>
// #include <bits/stdc++.h>
#define double long double
#define int long long int
#define ll int
#define ibs ios_base::sync_with_stdio(false)
#define cti cin.tie(0)
#define bp __builtin_popcount
#define pb emplace_back
#define koto_memory(a) cout<<(sizeof(a)/1048576.0)<<" MB";
#define res(v) sort(all(v)),v.erase(unique(all(v)), v.end());
#define timer cerr << "Time elapsed : " << 1.0 * clock() / CLOCKS_PER_SEC << " sec \n";
#define deb(x) cout<<"\n["<<#x<<" = "<<x<<"]\n";
using vi = std::vector<int>;
using vvi = std::vector<vi>;
using pii = std::pair<int,int>;
using vpii = std::vector<pii>;
using vvpii = std::vector<vpii>;
#define mp         make_pair
#define rep(i,a,b) for (int i = a; i <= b; i++)
#define per(i,b,a) for (int i = b; i >= a; i--)
#define all(x)     x.begin(), x.end()
using namespace std;
const int N=2e6+10;
const int inf = /*0x3f3f3f3f*/1e18+10;
// const ll M = 998244353 ; // Mulo
// const int M = 1e9+7 ; // Mulo
const double Pi = 3.14159265;
#define F first
#define S second
int n,ans;
void solve(){
  cin>>n;
  rep(i,1,n){
    ans+=(n/i);
    if(i*(n/i)==n)ans--;
  }
  cout<<ans;
}
int32_t main()
{
  ibs;cti;
  solve();return 0;
  /*,cout<<"\n"*/;
  // cout<<"\n";
  int xx=0;
  int t;cin>>t;while(t--){/*xx++;cout<<"Case "<<xx<<":\n"*/;solve();cout<<"\n";}
  return 0;
}