#include <fstream>
#define MAXN 1000005
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
 
int v[MAXN],n;
long long sol;
 
int main()
{
    int i,j;
    f>>n;
    for(i=2;i<=n;i++)
        v[i]=i-1;
    for(i=2;2*i<=n;i++)
        for(j=2*i;j<=n;j+=i)
            v[j]-=v[i];
    for(i=2;i<=n;i++)
        sol+=1LL*v[i];
    g<<sol*2+1<<'\n';
    f.close();
    g.close();
    return 0;
}