#include <iostream>
#include <fstream>
#define ull unsigned long long
using namespace std;
ifstream f ("fractii.in");
ofstream g ("fractii.out");
int n,i,j,v[1000005];
ull nr;
int main()
{
    f>>n;
    nr=1;
    for (i=2;i<=n;i++)
        v[i]=i-1;
    for (i=2;i<=n;i++)
    {
        nr+=2*v[i];
        for (j=2*i;j<=n;j+=i)
            v[j]-=v[i];
    }
    g<<nr;
    return 0;
}