#include<fstream>
using namespace std;

int N, fractii, prim[]={2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,181,191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,277,281,283,293,307,311,313,317,331,337,347,349,353,359,367,373,379,383,389,397,401,409,419,421,431,433,439,443,449,457,461,463,467,479,487,491,499,503,509,521,523,541,547,557,563,569,571,577,587,593,599,601,607,613,617,619,631,641,643,647,653,659,661,673,677,683,691,701,709,719,727,733,739,743,751,757,761,769,773,787,797,809,811,821,823,827,829,839,853,857,859,863,877,881,883,887,907,911,919,929,937,941,947,953,967,971,977,983,991,997,1009};
ifstream fin ("fractii.in");
ofstream fout ("fractii.out");

int indicatorEuler(int N)
{
	fractii = 1;
	int i = 0, p;
	while (prim[i]<1009 && N > 1)
	{
		if (N % prim[i] == 0)
		{
			p = 1;
			while (N % prim[i] == 0) 
			{
				p *= prim[i];
				N /= prim[i];
			}
			fractii *= (prim[i]-1)* (p / prim[i]);
		}
		i++;
	}
	if (N!=1) fractii *= N-1;
	return fractii;
}
int main()
{
	fin>>N;
	int i;
	long long sol=1;
	for (i = 2; i<=N ; i++) sol+=2*indicatorEuler(i);
	fout<<sol<<"\n";
	fin.close();
	fout.close();
	return 0;
}