#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int N,i,j,v[1000000];
int s;
int main()
{
    f>>N;
    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);
            }
        }
        s=s+v[i]*2;
    }
    g<<s+1;
    return 0;
}