#include <fstream>
using namespace std;
ifstream cin("fractii.in");
ofstream cout("fractii.out");
int main()
{
    unsigned long long n,i,cnt=0;
    cin >> n;
    for(i=2; i<=n; ++i)
    {
        unsigned long long p = i,x = i,d = 2;
        while (x != 1)
        {
            if (x % d == 0)
            {
                p /= d;
                p *= d - 1;
                while (x % d == 0)
                    x /= d;
            }
            if (d == 2) d = 3;
            else d += 2;
            if (d * d > x) d = x;
        }
        cnt+=p;
    }
    cout << 2*cnt+1;
    return 0;
}