#include <fstream>

using namespace std;

#define MAX 1000001

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

int main()
{
    long long v[MAX],i,j,n,x;
    fin>>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=j+i)
                    v[j]=(v[j]/i)*(i-1);
    for (i=2;i<=n;i++)
        x=x+v[i];
    fout<<2*x+1;
    return 0;
}