#include <cstdio>
#include<fstream>
using namespace std;
 ifstream fin("fractii.in");
 ofstream fout("fractii.out");
const int Max = 1000001;

int phi[Max];

int main()
{


    int N, i, j;
    long long Sum = 0;

    fin>>N;
    for(i = 1; i <= N; i++) phi[i] = i-1;
    for(i = 2; i <= N; i++)
        for(j = 2*i; j <= N; j+= i) phi[j] -= phi[i];

    for(i = 1; i <= N; i++) Sum += phi[i]*2;
    fout<<Sum+1;
    /*fout<<"\n";
    for(i=1;i<=N;i++)
        fout<<phi[i]<<" ";*/
    return 0;
}