#include <iostream>
#include <fstream>
using namespace std;
ifstream in ("fractii.in");
ofstream out("fractii.out");
long const N=1000005;
long long suma,v[N];
int main()
{
    long n;  in>>n;
    for(long i=1;i<=n;i++)
        v[i]=i;
    for(long i=2;i<=n;i++)
        if(v[i]==i)
            for(long j=i;j<=n;j+=i)
                v[j]=v[j]/i*(i-1);
    for(long i=2;i<=n;i++)
        suma+=v[i];
    out<<suma+suma+1<<"\n";
    return 0;
}