#include <fstream>

using namespace std;

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

const int N = 1000001;
int e[N];



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