#include<fstream>
#define N 1000000
using namespace std;
long long v[N], i, n, s;
void generate()
{
     for(i = 1; i <= n; ++i)
           v[i] = i;
     for(i = 2; i <= n; i++)
           if(v[i] == i)
                   for(int j = i; j <= n; j+=i)
                           v[j]=v[j]/i*(i-1);
}
int main() {
    ifstream f("fractii.in");
    ofstream g("fractii.out");
    f>>n;
    generate();
    for(i = 1; i <= n; i++)
          s+=v[i];
    g<<s*2-1;
    return 0;
}