#include <bits/stdc++.h>

using namespace std;
long long S, phi[1000005];
int x, y, N, i, j, r;
int main()
{
    freopen("fractii.in", "r", stdin);
    freopen("fractii.out", "w", stdout);
    for (i = 1; i <= 1000000; i++) phi[i] = i;
    for (i = 2; i <= 1000000; i++) {
            if (phi[i] == i)
            for (j = i; j<= 1000000; j += i) {
                phi[j] /= i;
                phi[j] *= (i-1);
            }
    }
    scanf("%d", &N);
    long long Sum = 0;
    for(i = 1; i <= N; i++) Sum += phi[i] * 2LL;
    printf("%lld", Sum - 1LL);
    return 0;
}