#include <fstream>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
int v[1000003];
int main(){
	long long n, s=0, i, j;
	in>>n;
	for(i=2; i<=n; i++){
		s+=(v[i]+=i-1);
		for(j=i+i; j<=n; j+=i)
			v[j]-=v[i];
	}
	out<<s+s+1;
	return 0;
}