[AHOI2005]COMMON 约数研究

https://www.luogu.org/problemnew/show/P1403

https://www.lydsy.com/JudgeOnline/problem.php?id=1968

题解：数论+朴素

/*
*@Author:   STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
using namespace std;
typedef long long ll;
const int N=10000;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,k,q;

int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif
    scanf("%d",&n);
    int ans=0;
    for(int i=1;i<=n;i++)ans+=n/i;
    cout<<ans;
    //cout << "Hello world!" << endl;
    return 0;
}