#include<fstream.h>

const int N=1000007;
int e[N];
void euler()
{
	for(int j=1;j<N;++j)
		e[j]=j;
	for(int i=2; i<N;++i)
		if(e[i]==i)
			for(int j=i; j<N; j+=i)
				e[j]=e[j]/i*(i-1);
}
int main()
{
	ifstream in("fractii.in");
	ofstream out("fractii.out");
	int n;
	in>>n;
	euler();
	long long s=0;
	for(int i=2;i<=n;++i)
		s+=(long long)e[i];
	out<<1+2*s<<"\n";
	in.close();
	out.close();
	return 0;
}