#include <iostream>
#include <fstream>
#define NMax 1000005
using namespace std;

ifstream fin("fractii.in");
ofstream fout("fractii.out");

long long fr[NMax],N,sol;

void read()
{
    fin>>N;
}

void solve()
{
    int i,j;
    for(i=1;i<=N;++i)
    {
        fr[i]=i-1;
    }
    for(i=2;i<=N;++i)
    {
        for(j=i+i;j<=N;j+=i)
        {
            fr[j]-=fr[i];
        }
    }
    for(i=2;i<=N;++i)
        sol+=fr[i];
    sol*=2;
    sol++;
}

void print()
{
    fout<<sol<<"\n";
}

int main()
{
    read();
    solve();
    print();
    return 0;
}