#include <iostream>
#include <fstream>
using namespace std;

float relprim(int x){
if(x==1) return 1;
else{
int d=2;
while(x%d!=0)
d++;
while(x%d==0)
x=x/d;
return relprim(x)*(d-1)/d;

}}

int main(){
ifstream f("fractii.in"); ofstream g("fractii.out");
int S=0;
int x; f>>x;
for(int i=2;i<=x;i++)
S=S+i*relprim(i);
S=2*S+1;
g<<S;
return false;}