#include <bits/stdc++.h>

using namespace std;

ifstream f("fractii.in");
ofstream g("fractii.out");

unsigned long long n,rez,i,j;

unsigned long long phi(unsigned long long n){
    unsigned long long rez=n;
    for(unsigned long long d=2;d*d<=n;d++){
        if(n%d==0)rez=rez/d*(d-1);
        while(n%d==0)n/=d;
    }
    if(n>1)rez=rez/n*(n-1);
    return rez;
}

int main()
{
    f>>n;
    rez=1;
    for(i=2;i<=n;i++)
        {
            rez=rez+2*phi(i);

        }
    g<<rez;
    return 0;
}