[Luogu p1403] Research on divisor

$link$

analysis ：

For each number $k(1<=k<=n)$$n$ The sum of the divisors of, i.e $k$ The sum of all multiples of

CODE：

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#define reg register
using namespace std;
typedef long long ll;
int n,ans;
int main(){
    
	scanf("%d",&n);
	for(int i=1;i<=n;i++)
		ans+=n/i;
	printf("%d",ans);
	return 0;
}