#include <fstream>
#define int long long
using namespace std;
ifstream in ("fractii.in");
ofstream out ("fractii.out");
int v[1000001],prim[1000001];
main ()
{
    int n,s=0;
    in>>n;
    for (int i = 1;i<=n;++i)
        v[i]=i;
    for (int i = 2;i<=n;++i)
        if (prim[i]==0)
            for (int j = i;j<=n;j+=i)
                v[j]=v[j]/i,v[j]*=i-1,prim[j]=1;
    for (int i = 2;i<=n;++i)
        s+=v[i];
    out<<s*2+1;
}