#include <iostream>
#include<fstream>
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
const int NMAX=1000001;
int v[NMAX];
int main()
{
    long long n,i,s,j;
    fin>>n;
    for( i=2;i<=n;i++)
        v[i]=i-1;
    for( i=2;i<=n;i++)
    {
        s=s+v[i];
        for( j=2*i;j<=n;j+=i)
            v[j]-=v[j]-v[i];
    }
    fout<<s*2+1 << '\n';
    return 0;
}