#include <iostream>
#include <fstream>
#include <math.h>

using namespace std;
bool c[500000];
int v[100],u,x;

int euller(int y)
    {
        int i=0;
        int inainte=y;
        while(y!=1)
            {if(y%v[i]==0)
                {inainte=inainte*(v[i]-1)/v[i];
                while(y%v[i]==0)
                    y=y/v[i];
                }
             i++;
            }
        return inainte;

    }

void ciur()
{   bool c[1000000];
    int i,j;
    u=1;
    v[0]=2;

    for(i=3;i<=x;i=i+2)
        if(!c[i])
        {c[i]=true;
        v[u]=i;
        u++;
        for(j=i;j<=x;j=j+i)
            c[j]=true;
        }



}


int main()
{
    int i,cate=0;
    ifstream fin("fractii.in");
    ofstream fout("fractii.out");
    fin>>x;
    ciur();
    for(i=1;i<=x;i++)
        cate=cate+euller(i);
    fout<<cate*2-1;






    return 0;
}