#include <stdio.h>
#include <vector>
using namespace std;
const int prime[168]={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};
long long tot[1000010];

int main()
{
	int i, k, x, N, g;
	long long sol, n, pow;

	//int v[200];
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	scanf("%d", &N);
	sol = 1;
	tot[1] = 1;
	for (x = 2; x <= N; ++ x)
	{
		k = x;
		n = 0;
//		v[0] = 0;
		g = 1;
		for (i = 0; i <= 167; ++ i)
			if (k%prime[i]== 0)
			{
				//v[++v[0]]=prime[i];
				//n = n-(n/prime[i]);
				pow = 1;
				while (k%prime[i] == 0)
				{
					k/=prime[i];
					pow =(long long)pow * prime[i];
				}
				pow /= prime[i];
				n = (long long)tot[k] * pow * (prime[i]-1);
				g = 0;
				break;
			}
		
		if ( g)
		{
			n = x-1;
		}
		tot[x] = n;
		sol=(long long)sol + n;
	}
	printf("%lld\n",(sol*2)-1);
	return 0;
}