#include <bits/stdc++.h>

using namespace std;

ifstream fin("fractii.in");
ofstream fout("fractii.out");

int phi[1000002];
int n;
unsigned long long s;

void phi_calc()
{
    for(int i=1; i<=n; i++)
        phi[i]=i;
    for(int i=2; i<=n; i++)
        if(phi[i]==i)
    {
        for(int j=i; j<=n; j+=i)
            phi[j]=phi[j]-phi[j]/i;
    }
}

int main()
{
    int i, j;
    fin>>n;
    phi_calc();
    for(i=1; i<=n; i++)
        s+=(unsigned long long)phi[i];
    fout<<(unsigned long long)2*s-1<<'\n';
    return 0;
}