#include <fstream>

using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int v[1000002],i,n,j;
unsigned long long s;
int main()
{
    fin>>n;
    v[1]=1;
    for(i=2;i<=n;i++)
        if(v[i]==0)
        {
            v[i]=i-1;
            for(j=i*2;j<=n;j=j+i)
            {
             if(v[j]==0)
                v[j]=j/i*(i-1);
            else
                v[j]=v[j]/i*(i-1);
            }
        }
    for(i=2;i<=n;i++)
        s+=v[i];
    fout<<2*s+1<<'\n';
    return 0;
}