#include <bits/stdc++.h>
#define in "fractii.in"
#define out "fractii.out"
#define MAXN 1000005
using namespace std;
ifstream fin(in);
ofstream fout(out);

int v[MAXN],n;
long long sol;

int main()
{
    int i,j;

    fin>>n;

    for (i=2;i<=n;i++) v[i]=i-1;
    for (i=2;2*i<=n;i++) for (j=2*i; j<=n; j+=i) v[j]-=v[i];
    for (i=2;i<=n;i++) sol+=1LL*v[i];
    fout<<sol*2+1<<"\n";

    fin.close();
    fout.close();
    return 0;
}