#include <cstdio>
#include <cstring>
#include <algorithm>
#define maxN 10000002
using namespace std;
long long n, i, j, v[maxN], sol;
void read()
{
    freopen("fractii.in", "r", stdin);
    scanf("%lld", &n);
    v[1] = 1;
    sol = 1;
}
void solve()
{
    for (i = 2; i <= n; ++ i)
        v[i] = i - 1;
    for (i = 2; i <= n; ++ i)
    {
        sol += 2 * v[i] * 1LL;
        for (j = i * 2; j <= n; j += i)
            v[j] -= v[i];
    }
}
void write()
{
    freopen("fractii.out", "w", stdout);
    printf("%lld", sol);
}
int main()
{
    read();
    solve();
    write();
    return 0;
}