#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
long long x[1000001], n, i, j, nr;
int main()
{
    f>>n;
    for(i=2;i<=n;i++)
        x[i]=i-1;
    for(i=2;i<=n;i++)
    {
        nr+=x[i];
        for(j=i+i;j<=n;j+=i)
            x[j]-=x[i];
    }
    g<<nr+nr+1<<'\n';
    return 0;
}