#include <bits/stdc++.h>

using namespace std;

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

int main()
{
    int n;
    long long v[1000003],sum=0;
    fin>>n;
    for(int i=1;i<=n;++i)v[i]=i;
    for(int i=2;i<=n;++i){
        if(v[i]==i)
            for(int j=2*i;j<=n;j+=i)
                v[j]=v[j]*(i-1)/i;
        sum+=(v[i]==i?i-1:v[i]);
    }
    fout<<2*sum+1<<'\n';
    return 0;
}