#include<fstream> 
using namespace std; 
long long sir[1000010]; 
int main() 
{long n,i,j; 
long long cont; 
ifstream f1("fractii.in"); 
ofstream f2("fractii.out"); 
f1>>n; 
cont=0; 
for(i=1;i<=n;++i) 
	sir[i]=i; 
for(i=2;i<=n;++i)
	if(sir[i]==i) 
		{j=1; 
		while (i*j<=n) 
			{sir[i*j]=sir[i*j]*(i-1)/i; 
			j=j+1;
			} 
		} 
for (i=2; i<=n; i++) 
	cont+=sir[i]; 
cont=cont*2; 
    
cont++;   
f2<<cont<<endl; 
 
 

return 0; 
}