#include <bits/stdc++.h>
using namespace std;

ifstream fin("fractii.in");
ofstream fout("fractii.out");
int n,nr,v[1000001];
int main()
{
    fin>>n;
    for(int i=2;i<=n;i++)
        v[i]=i-1;
    for(int i=2;i<=n;i++)
    {
        nr+=v[i];
        for(int j=2*i;j<=n;j+=i)
            v[j]-=v[i];
    }
    fout<<nr*2+1 << endl;
    return 0;
}