using namespace std;
#include <fstream>
#define NMAX 1000005
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int N;
long tot[NMAX];
long long S;
int main(void)
{
int i, j;
fin>>N;
for(i=1;i<=N;i++)
tot[i]=i;
for (i = 2; i <= N; ++i)
if (tot[i]==i)
{
tot[i]=i-1;
for (j = i+i; j <= N; j += i)
tot[j]=tot[j]/i*(i-1);
}
for(i=1;i<=N;i++)
S=S+1LL*tot[i];
}