#include <iostream>
#include <cstdio>
#include <bitset>
#define MAXN 1000050

using namespace std;

bitset<MAXN> ciur;
long long tot[MAXN], rez;
int n;

void solve()
{
	for (int i = 1; i <= n; i++)
		tot[i] = i;
    for (int i = 2; i <= n; i++) {
        if (!ciur[i]) {
			for (int j = i; j <= n; j+=i) {
                ciur[j] = 1;
                tot[j] *= (i-1);
                tot[j] /= i;
			}
        }
    }
}

int main()
{
    freopen("fractii.in", "r", stdin);
    freopen("fractii.out", "w", stdout);

	scanf("%d", &n);
    solve();
    for (int i = 1; i <= n; i++)
		rez += tot[i];
	printf("%lld", 2*rez-1);

    return 0;
}