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