using namespace std;
#include<fstream>
int n,i,j,v[10000001];
long long numar=0;
int main()
{
 
 
ifstream fin("fractii.in");   
ofstream fout("fractii.out");
fin>>n;

for(i=2;i<=n;i++)
v[i]=i-1;
for(i=2;i<=n;i++){
numar=numar+v[i];    
for(j=2*i;j<=n;j+=i)

v[j]-=v[i];
}
numar=numar*2+1;
fout<<numar;
 
return 0;
}