#include <fstream>

using namespace std;

ifstream cin("fractii.in");
ofstream cout("fractii.out");
int f[1000002];
int main()
{
    int n,i,j;
    long long sum=0;
    cin>>n;
    for(i=1; i<=n; i++)
        f[i]=i;
    for(i=2; i<=n; i++)
    {
        if(f[i]==i)
        {
            f[i]=i-1;
            for(j=2*i; j<=n; j+=i)
            {
                f[j]=f[j]/i*(i-1);
            }
        }
    }
    ///indicatorul lui Euler pt toate nr mai mici ca n
    for(i=2;i<=n;i++)
        sum+=f[i]*2;
    cout<<sum+1;
    return 0;
}