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