#include <fstream>
#define MAXN  1000000
using namespace std;
ifstream in ("fractii.in");
ofstream out ("fractii.out");
int e[MAXN+5];
void euler()
{
    for(int i=2;i<=MAXN;i++)
        e[i] = i;
    for(int i=2; i<=MAXN; i++)
    {
        if(e[i] == i)
            for(int j=i;j<=MAXN;j+=i)
                e[j] = e[j] / i * (i-1);
    }
}
int main()
{
    int n,i;
    long long s=1;
    euler();
    in>>n;
    for(i=1;i<=n;i++)
        s += 2*e[i];
    out<<s;
    return 0;
}