#include <fstream>
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
bool b[1000001];
int v[1000001];
int euler(int x)
{
if (b[x] == 0)
return x-1;
int rasp = x;
int i = 1;
while (v[i] * v[i] <= x)
{
if (x%v[i] == 0)
{
rasp = 1ll * rasp * (v[i]-1)/v[i];
while (x%v[i] == 0)
x = x/v[i];
}
i++;
}
if (x > 1)
rasp = 1ll*rasp * (x-1)/x;
return rasp;
}
int main()
{
int i, j, n;
long long nr = 0;
b[0] = b[1] = 1;
for (i = 2; i<=1000; i++)
if (b[i] == 0)
for (j = i*i; j<=1000000; j=j+i)
b[j] = 1;
for (i = 1; i<=1000000; i++)
if (b[i] == 0)
v[++v[0]] = i;
fin >> n;
for (i = 2; i<=n; i++)
nr = nr + euler(i);
fout << 2*nr + 1;
return 0;
}