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

long n,s=0;
long phi[1000001];
void cit()
{
    ifstream f;
    f.open("fractii.in");
    f>>n;
    f.close();
}
int main()
{
    cit();
    for (long i=2;i<=n;++i)
        phi[i]=i-1;
    for (long i=2;i<=n;++i)
    {
        s+=phi[i];
        for (long j=2*i;j<=n;j+=i)
            phi[j]-=phi[i];
    }
    ofstream g;
    g.open("fractii.out");
    g<<2*s+1<<+"\n";
    g.close();
    return 0;
}