【题目分析】
狄利克雷卷积。
然后直接求出欧拉函数，计算和即可。
【代码】
#include <cstdio>
#include <cstring>
#include <cmath>
#include <cstdlib>
#include <map>
#include <set>
#include <queue>
#include <string>
#include <iostream>
#include <algorithm>
using namespace std;
#define maxn 500005
#define ll long long
#define inf 0x3f3f3f3f
#define F(i,j,k) for (int i=j;i<=k;++i)
#define D(i,j,k) for (int i=j;i>=k;--i)
void Finout()
{
#ifndef ONLINE_JUDGE
freopen("in.txt","r",stdin);
// freopen("out.txt","w",stdout);
#endif
}
int Getint()
{
int x=0,f=1; char ch=getchar();
while (ch<'0'||ch>'9') {if (ch=='-') f=-1; ch=getchar();}
while (ch>='0'&&ch<='9') {x=x*10+ch-'0'; ch=getchar();}
return x*f;
}
int n;
int phi(int x)
{
// cout<<"phi"<<x;
int ret=x;
F(i,2,sqrt(x))
{
if (x%i==0) ret/=i,ret*=(i-1);
while (x%i==0) x/=i;
}
if (x>1) ret=ret/x*(x-1);
// cout<<" is "<<ret<<endl;
return ret;
}
ll ans=0;
int main()
{
Finout();
n=Getint();
F(i,1,sqrt(n)) if (n%i==0)
{
ans+=(ll)phi(i)*(n/i);
if (i*i<n) ans+=(ll)phi(n/i)*i;
}
cout<<ans<<endl;
}