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

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

long long v[1000000];
int main()
{

    long long suma=0;
    int n, i, j;
    in>>n;
    for(i=1; i<=n; ++i)
        v[i]=i;
    for(i=2; i<=n; ++i)
    {
        if(v[i]==i)
            for(j=i; j<=n; j+=i)
                v[j]=v[j]/i*(i-1);
        suma+=v[i];
    }
    out<<suma*2+1;
    return 0;
}