#include<fstream> 
using namespace std; 
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; 
}