#include <fstream.h>

int main()
{
	long N, i, j, phi[1000001];
	unsigned long S=1;
	ifstream fin;
	fin.open("fractii.in");
	fin>>N;
	fin.close();
	for (i=1; i<=N; i++)
	{
		phi[i]=i;
	}
	for (i=2; i<=N; i++)
	{
		if (phi[i]==i)
		{
			for (j=i; j<=N; j+=i)
			{
				phi[j]/=i;
				phi[j]*=(i-1);
			}
		}
	}
	for (i=2; i<=N; i++)
	{
		S+=2*phi[i];
	}
	ofstream fout;
	fout.open("fractii.out");
	fout<<S;
	fout.close();
	return 0;
}