#include <iostream>
#include<fstream>
using namespace std;
long long i,j,n,v[1001000];
long long s;
int main()
{
    ifstream f("fractii.in");f>>n;
    f.close();
    for(i=0;i<n;)v[++i]=i;
    ++n;
    for(i=2;i<n;++i)
    {
        if(v[i]==i)
        {
            for(j=i;j<n;j+=i)
                v[j]=v[j]*(i-1)/i;
        }
        s+=v[i];
    }
    s*=2;
    ++s;
    ofstream g("fractii.out");
    g<<s;
    g.close();
    return 0;
}