#include <bits/stdc++.h>
#define InFile "fractii.in"
#define OutFile "fractii.out"
#define DMAX 1000010

using namespace std;

FILE *fin=fopen(InFile,"r");
FILE *fout=fopen(OutFile,"w");

int ind_eul[DMAX];
int n;
long long int cate;

void euler();

int main()
{fscanf(fin,"%d",&n);
 euler();
 for(int i=1;i<=n;i++)
     cate+=2*ind_eul[i];
 fprintf(fout,"%lld\n",cate-1);
 return 0;
}
void euler()
{int i,j;
 ind_eul[1]=1;
 for(i=2;i<=n;i++)
     ind_eul[i]=i-1;
 for(i=2;i<=n;i++)
    for(j=2*i;j<=n;j+=i)
        ind_eul[j]-=ind_eul[i];
}