#include <fstream>
using namespace std;

ifstream f("fractii.in");
ofstream g("fractii.out");
int v[1000005],n,nr,d;
long long r=1;
int main()
{
    f>>n;
    for(int i=1;i<=n;++i)v[i]=i-1;
    for(int i=2;i<=n;++i)
        for(int j=i*2;j<=n;j+=i)v[j]-=v[i];
    for(int i=1;i<=n;++i)r+=v[i]*2;
    g<<r;
    return 0;
}