Research on lg1403 divisor

Title Description

Xiao Lian is studying some problems related to divisor recently , He counts every positive number N The number of divisors of , And f(N) To express . for example 12 The number of divisors is 1、2、3、4、6、12. therefore f(12)=6.f(n) Express n The approximate number of , Now give n, Ask for f(1) To f(n) The sum of .

Input format ：

The input line , An integer n

Output format ：

Output an integer , Represents the sum

sample input #1：3

sample output #1：5

thinking: Write the program on the first day after the holiday , I wrote two math problems , And this is not so simple , The key is function f(i) = n/i The determination of , This problem is transformed into , Find the sum of all the factors , Is to find that each number factor is 1 The number of and ( n/1 ), Each number factor is 2 The number of and ( n/2 ),…… So the result came out , It's easy to know the answer, isn't it , But I didn't think of it ... thank

#include<iostream>
using namespace std;
int n,ans;
int main(void){
    cin>>n;
    for(int i=1;i<=n;i++)
        ans+=n/i;
    cout<<ans;
}