#include <bits/stdc++.h>

using namespace std;

ifstream fin("fractii.in");
ofstream fout("fractii.out");
long long n, i;
int p[1000002];

static inline long long Phi(long long n) {
    long long r = 0;
    for(int i = 2; i <= n; i++) p[i] = i;
    for(int i = 2; i <= n; i++) {
        if(p[i] == i) {
            for(int j = i; j <= n; j += i) p[j] = p[j] / i * (i - 1);
        }
        r += p[i];
    }
    return r;
}

int main() {
    fin >> n;
    fout << Phi(n) * 2 + 1;

    return 0;
}