#include <fstream>
using namespace std;

const int MAXN = 1000001;
int phi[MAXN];

void calculatePhi(int n) {
    // Initialize phi array
    for (int i = 1; i <= n; i++)
        phi[i] = i;

    // Calculate Euler's totient for all numbers up to n
    for (int i = 2; i <= n; i++) {
        if (phi[i] == i) {  // i is prime
            for (int j = i; j <= n; j += i) {
                phi[j] = phi[j] / i * (i - 1);
            }
        }
    }
}

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

    int n;
    fin >> n;

    calculatePhi(n);

    long long sum = 0;
    for (int i = 1; i <= n; i++) {
        sum += phi[i];
    }

    fout << sum;

    return 0;
}