#include <bits/stdc++.h>

using namespace std;

#define USE_STD_IO 0
#if USE_STD_IO
    #define fin cin
    #define fout cout
#else
    ifstream fin("fractii.in");
    ofstream fout("fractii.out");
#endif

const int MAX = 1000000;
int n, i, j, phi[MAX + 2];

long long rasp;

int main() {
    if(USE_STD_IO) ios_base::sync_with_stdio(false);
    fin.tie(NULL);
    fout.tie(NULL);

    fin >> n;
    for(i = 1; i <= n; i++) phi[i] = i;
    for(i = 2; i <= MAX; i++) {
        if(i == phi[i]) {
            for(j = i; j <= MAX; j += i) {
                phi[j] = phi[j] / i * (i - 1);
            }
        }

        rasp += phi[i];
    }

    fout << rasp * 2 + 1;

    return 0;
}