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